diff --git a/chrome/content/zotero/xpcom/db.js b/chrome/content/zotero/xpcom/db.js
index a37ee98a1..4b85fc2ae 100644
--- a/chrome/content/zotero/xpcom/db.js
+++ b/chrome/content/zotero/xpcom/db.js
@@ -581,7 +581,7 @@ Zotero.DBConnection.prototype.checkException = function (e) {
 }
 
 
-Zotero.DBConnection.prototype.backupDatabase = function () {
+Zotero.DBConnection.prototype.backupDatabase = function (suffix) {
 	if (this.transactionInProgress()) {
 		this._debug("Transaction in progress--skipping backup of DB '" + this._dbName + "'", 2);
 		return false;
@@ -597,7 +597,8 @@ Zotero.DBConnection.prototype.backupDatabase = function () {
 	this._debug("Backing up database '" + this._dbName + "'");
 	
 	var file = Zotero.getZoteroDatabase(this._dbName);
-	var backupFile = Zotero.getZoteroDatabase(this._dbName, 'bak');
+	var backupFile = Zotero.getZoteroDatabase(this._dbName,
+		(suffix ? suffix + '.' : '') + 'bak');
 	
 	// Copy via a temporary file so we don't run into disk space issues
 	// after deleting the old backup file
@@ -626,6 +627,9 @@ Zotero.DBConnection.prototype.backupDatabase = function () {
 		}
 		catch (e){
 			this._debug("Database file '" + tmpFile.leafName + "' is corrupt--skipping backup");
+			if (tmpFile.exists()) {
+				tmpFile.remove(null);
+			}
 			return false;
 		}
 	}
@@ -681,18 +685,6 @@ Zotero.DBConnection.prototype._getDBConnection = function () {
 		}
 	}
 	
-	// DEBUG: Temporary check
-	// Test the backup file (to make sure the backup mechanism is working)
-	if (backupFile.exists()) {
-		try {
-			this._connection = store.openDatabase(backupFile);
-		}
-		catch (e) {
-			this._debug("Backup file '" + backupFile.leafName + "' was corrupt!", 1);
-		}
-		this._connection = undefined;
-	}
-	
 	catchBlock: try {
 		var corruptMarker = Zotero.getZoteroDatabase(this._dbName, 'is.corrupt');
 		if (corruptMarker.exists()) {
diff --git a/chrome/content/zotero/xpcom/schema.js b/chrome/content/zotero/xpcom/schema.js
index 611c6a34c..a2833e666 100644
--- a/chrome/content/zotero/xpcom/schema.js
+++ b/chrome/content/zotero/xpcom/schema.js
@@ -46,6 +46,13 @@ Zotero.Schema = new function(){
 		
 		var schemaVersion = _getSchemaSQLVersion('userdata');
 		
+		Zotero.UnresponsiveScriptIndicator.disable();
+		
+		// If upgrading userdata, make backup of database first
+		if (dbVersion < schemaVersion){
+			Zotero.DB.backupDatabase(dbVersion);
+		}
+		
 		Zotero.DB.beginTransaction();
 		
 		try {
@@ -65,9 +72,9 @@ Zotero.Schema = new function(){
 				 }
 			}
 			
-			_migrateUserDataSchema(dbVersion);
-			var up1 = _updateSchema('system');
-			var up2 = _updateSchema('scrapers');
+			var up1 = _migrateUserDataSchema(dbVersion);
+			var up2 = _updateSchema('system');
+			var up3 = _updateSchema('scrapers');
 			
 			// Rebuild fulltext cache if necessary
 			if (Zotero.Fulltext.cacheIsOutdated()){
@@ -78,16 +85,36 @@ Zotero.Schema = new function(){
 		catch(e){
 			Zotero.debug(e);
 			Zotero.DB.rollbackTransaction();
+			Zotero.UnresponsiveScriptIndicator.enable();
 			throw(e);
 		}
 		
-		if (up1 || up2) {
+		if (up1) {
+			// Upgrade seems to have been a success -- delete any previous backups
+			var maxPrevious = dbVersion - 1;
+			var file = Zotero.getZoteroDirectory();
+			// directoryEntries.hasMoreElements() throws an error (possibly
+			// because of the temporary SQLite journal file?), so we just look
+			// for all versions
+			for (var i=maxPrevious; i>=29; i--) {
+				var fileName = 'zotero.sqlite.' + i + '.bak';
+				file.append(fileName);
+				if (file.exists()) {
+					Zotero.debug('Removing previous backup file ' + fileName);
+					file.remove(null);
+				}
+				file = file.parent;
+			}
+		}
+		
+		if (up2 || up3) {
 			// Run a manual scraper update if upgraded and pref set
 			if (Zotero.Prefs.get('automaticScraperUpdates')){
 				this.updateScrapersRemote(2);
 			}
 		}
 		
+		Zotero.UnresponsiveScriptIndicator.enable();
 		return;
 	}
 
@@ -914,6 +941,8 @@ Zotero.Schema = new function(){
 			alert('Error migrating Zotero database');
 			throw(e);
 		}
+		
+		return true;
 	}
 	
 	
diff --git a/chrome/content/zotero/xpcom/zotero.js b/chrome/content/zotero/xpcom/zotero.js
index 4575db66e..efd434950 100644
--- a/chrome/content/zotero/xpcom/zotero.js
+++ b/chrome/content/zotero/xpcom/zotero.js
@@ -235,6 +235,10 @@ var Zotero = new function(){
 			var file = Components.classes["@mozilla.org/file/local;1"].
 				createInstance(Components.interfaces.nsILocalFile);
 			file.persistentDescriptor = Zotero.Prefs.get('dataDir');
+			if (!file.exists()) {
+				var e = { name: "NS_ERROR_FILE_NOT_FOUND" };
+				throw (e);
+			}
 		}
 		else {
 			var file = Zotero.getProfileDirectory();