diff --git a/chrome/content/zotero/xpcom/storage/queue.js b/chrome/content/zotero/xpcom/storage/queue.js
index 2a12b23c4..941e79e50 100644
--- a/chrome/content/zotero/xpcom/storage/queue.js
+++ b/chrome/content/zotero/xpcom/storage/queue.js
@@ -104,9 +104,11 @@ Zotero.Sync.Storage.Queue.prototype.__defineSetter__('finishedRequests', functio
 		var localChanges = this._localChanges;
 		var remoteChanges = this._remoteChanges;
 		var conflicts = this._conflicts.concat();
+		var deferred = this._deferred;
 		this._localChanges = false;
 		this._remoteChanges = false;
 		this._conflicts = [];
+		this._deferred = null;
 		
 		if (!this._error) {
 			Zotero.debug("Resolving promise for queue " + this.name);
@@ -114,7 +116,7 @@ Zotero.Sync.Storage.Queue.prototype.__defineSetter__('finishedRequests', functio
 			Zotero.debug(this._remoteChanges);
 			Zotero.debug(this._conflicts);
 			
-			this._deferred.resolve({
+			deferred.resolve({
 				libraryID: this.libraryID,
 				type: this.type,
 				localChanges: localChanges,
@@ -128,7 +130,7 @@ Zotero.Sync.Storage.Queue.prototype.__defineSetter__('finishedRequests', functio
 			this._error = false;
 			e.libraryID = this.libraryID;
 			e.type = this.type;
-			this._deferred.reject(e);
+			deferred.reject(e);
 		}
 		
 		return;
@@ -368,7 +370,12 @@ Zotero.Sync.Storage.Queue.prototype.addConflict = function (requestName, localDa
 
 Zotero.Sync.Storage.Queue.prototype.error = function (e) {
 	if (!this._error) {
-		this._error = e;
+		if (this.isRunning()) {
+			this._error = e;
+		}
+		else {
+			Zotero.debug("Queue " + this.name + " was no longer running -- not assigning error", 2);
+		}
 	}
 	Zotero.debug(e, 1);
 	this.stop();
diff --git a/chrome/content/zotero/xpcom/storage/request.js b/chrome/content/zotero/xpcom/storage/request.js
index 080bd87e5..44e091af8 100644
--- a/chrome/content/zotero/xpcom/storage/request.js
+++ b/chrome/content/zotero/xpcom/storage/request.js
@@ -43,6 +43,7 @@ Zotero.Sync.Storage.Request = function (name, callbacks) {
 	
 	this._deferred = Q.defer();
 	this._running = false;
+	this._stopping = false;
 	this._percentage = 0;
 	this._remaining = null;
 	this._maxSize = null;
@@ -222,16 +223,16 @@ Zotero.Sync.Storage.Request.prototype.start = function () {
 		// This promise updates localChanges/remoteChanges on the queue
 		self._deferred.resolve(results);
 	})
-	.fail(function (e) {
+	.catch(function (e) {
+		if (self._stopping) {
+			Zotero.debug("Skipping error for stopping request " + self.name);
+			return;
+		}
 		Zotero.debug(self.queue.Type + " request " + self.name + " failed");
-		Zotero.debug(self._deferred);
-		Zotero.debug(self._deferred.promise.isFulfilled());
 		self._deferred.reject(e);
-		Zotero.debug(self._deferred.promise.isFulfilled());
-		Zotero.debug(self._deferred.promise.isRejected());
 	})
 	// Finish the request (and in turn the queue, if this is the last request)
-	.fin(function () {
+	.finally(function () {
 		if (!self._finished) {
 			self._finish();
 		}
@@ -309,6 +310,8 @@ Zotero.Sync.Storage.Request.prototype.onProgress = function (channel, progress,
  */
 Zotero.Sync.Storage.Request.prototype.stop = function () {
 	if (this.channel) {
+		this._stopping = true;
+		
 		try {
 			Zotero.debug("Stopping request '" + this.name + "'");
 			this.channel.cancel(0x804b0002); // NS_BINDING_ABORTED
@@ -343,7 +346,7 @@ Zotero.Sync.Storage.Request.prototype._finish = function () {
 		this.queue.updateProgress();
 	}
 	catch (e) {
-		Zotero.debug(e);
+		Zotero.debug(e, 1);
 		Components.utils.reportError(e);
 		this._deferred.reject(e);
 		throw e;
diff --git a/chrome/content/zotero/xpcom/storage/webdav.js b/chrome/content/zotero/xpcom/storage/webdav.js
index 9b4002e2c..8180e9c05 100644
--- a/chrome/content/zotero/xpcom/storage/webdav.js
+++ b/chrome/content/zotero/xpcom/storage/webdav.js
@@ -42,14 +42,19 @@ Zotero.Sync.Storage.WebDAV = (function () {
 	 * @param	{Zotero.Item}	item
 	 * @param	{Function}		callback		Callback f(item, mdate)
 	 */
-	function getStorageModificationTime(item) {
+	function getStorageModificationTime(item, request) {
 		var funcName = "Zotero.Sync.Storage.WebDAV.getStorageModificationTime()";
 		
 		var uri = getItemPropertyURI(item);
 		
-		return Zotero.HTTP.promise(
-				"GET", uri, { debug: true, successCodes: [200, 300, 404] }
-			)
+		return Zotero.HTTP.promise("GET", uri,
+			{
+				debug: true,
+				successCodes: [200, 300, 404],
+				requestObserver: function (xmlhttp) {
+					request.setChannel(xmlhttp.channel);
+				}
+			})
 			.then(function (req) {
 				checkResponse(req);
 				
@@ -163,7 +168,7 @@ Zotero.Sync.Storage.WebDAV = (function () {
 		var request = data.request;
 		var item = Zotero.Sync.Storage.getItemFromRequestName(request.name);
 		
-		return getStorageModificationTime(item)
+		return getStorageModificationTime(item, request)
 			.then(function (mdate) {
 				if (!request.isRunning()) {
 					Zotero.debug("Upload request '" + request.name
@@ -812,7 +817,7 @@ Zotero.Sync.Storage.WebDAV = (function () {
 		}
 		
 		// Retrieve modification time from server to store locally afterwards 
-		return getStorageModificationTime(item)
+		return getStorageModificationTime(item, request)
 			.then(function (mdate) {
 				if (!request.isRunning()) {
 					Zotero.debug("Download request '" + request.name
diff --git a/chrome/content/zotero/xpcom/storage/zfs.js b/chrome/content/zotero/xpcom/storage/zfs.js
index aecbb36a9..e32c1d817 100644
--- a/chrome/content/zotero/xpcom/storage/zfs.js
+++ b/chrome/content/zotero/xpcom/storage/zfs.js
@@ -38,10 +38,17 @@ Zotero.Sync.Storage.ZFS = (function () {
 	 * @param	{Zotero.Item}	item
 	 * @param	{Function}		callback		Callback f(item, etag)
 	 */
-	function getStorageFileInfo(item) {
+	function getStorageFileInfo(item, request) {
 		var funcName = "Zotero.Sync.Storage.ZFS.getStorageFileInfo()";
 		
-		return Zotero.HTTP.promise("GET", getItemInfoURI(item), { successCodes: [200, 404], headers: _headers })
+		return Zotero.HTTP.promise("GET", getItemInfoURI(item),
+			{
+				successCodes: [200, 404],
+				headers: _headers,
+				requestObserver: function (xmlhttp) {
+					request.setChannel(xmlhttp.channel);
+				}
+			})
 			.then(function (req) {
 				if (req.status == 404) {
 					return false;
@@ -72,10 +79,15 @@ Zotero.Sync.Storage.ZFS = (function () {
 				
 				return info;
 			})
-			.fail(function (e) {
+			.catch(function (e) {
 				if (e instanceof Zotero.HTTP.UnexpectedStatusException) {
-					var msg = "Unexpected status code " + e.xmlhttp.status
-						+ " getting storage file info";
+					if (e.xmlhttp.status == 0) {
+						var msg = "Request cancelled getting storage file info";
+					}
+					else {
+						var msg = "Unexpected status code " + e.xmlhttp.status
+							+ " getting storage file info";
+					}
 					Zotero.debug(msg, 1);
 					Zotero.debug(e.xmlhttp.responseText);
 					Components.utils.reportError(msg);
@@ -102,7 +114,7 @@ Zotero.Sync.Storage.ZFS = (function () {
 		
 		var request = data.request;
 		var item = Zotero.Sync.Storage.getItemFromRequestName(request.name);
-		return getStorageFileInfo(item)
+		return getStorageFileInfo(item, request)
 			.then(function (info) {
 				if (request.isFinished()) {
 					Zotero.debug("Upload request '" + request.name
@@ -694,7 +706,7 @@ Zotero.Sync.Storage.ZFS = (function () {
 		}
 		
 		// Retrieve file info from server to store locally afterwards
-		return getStorageFileInfo(item)
+		return getStorageFileInfo(item, request)
 			.then(function (info) {
 				if (!request.isRunning()) {
 					Zotero.debug("Download request '" + request.name