--- /usr/share/univention-management-console-frontend/js/umc/modules/computerroom.js.bak	2012-10-04 10:42:46.000000000 +0200
+++ /usr/share/univention-management-console-frontend/js/umc/modules/computerroom.js	2012-10-04 12:18:14.000000000 +0200
@@ -98,6 +98,8 @@
 	_currentSchool: null,
 	_currentRoom: null,
 
+	_nUpdateFailures: 0,
+
 	_vncEnabled: false,
 
 	uninitialize: function() {
@@ -606,6 +608,36 @@
 		this.changeRoom();
 	},
 
+	_acquireRoom: function(school, room, promptAlert) {
+		promptAlert = promptAlert === undefined || promptAlert;  // default value == true
+		return umc.tools.umcpCommand('computerroom/room/acquire', {
+			school: school,
+			room: room
+		}).then(dojo.hitch(this, function(response) {
+			if ( response.result.success === false ) {
+				// we could not acquire the room
+				if (promptAlert) {
+					// prompt a message if wanted
+					if ( response.result.message == 'ALREADY_LOCKED' ) {
+						umc.dialog.alert(this._('Failed to open a new session for the room.'));
+					} else if ( response.result.message == 'EMPTY_ROOM' ) {
+						umc.dialog.alert( this._( 'The room is empty or the computers are not configured correctly. Please select another room.' ) );
+					}
+				}
+				throw new Error('Could not acquire room');
+			}
+			this._currentRoom = room;
+			this._currentSchool = school;
+
+			// reload the grid
+			this.queryRoom();
+
+			// update the header text containing the room
+			this._updateHeader(room);
+			this._grid._updateFooterContent();
+		}));
+	},
+
 	changeRoom: function() {
 		// define a cleanup function
 		var dialog = null, form = null, okButton = null;
@@ -636,7 +668,7 @@
 			// show confirmation dialog if room is already locked
 			var room = _getRoom(vals.room);
 			if (room.locked) {
-				deferred = 	umc.dialog.confirm(this._('This computer room is currently in use by %s. You can take control over the room, however, the current teacher will be prompted a notification and its session will be closed.', room.user), [{
+				deferred = umc.dialog.confirm(this._('This computer room is currently in use by %s. You can take control over the room, however, the current teacher will be prompted a notification and its session will be closed.', room.user), [{
 					name: 'cancel',
 					label: this._('Cancel'),
 					'default': true
@@ -651,35 +683,12 @@
 				});
 			}
 
-			deferred = deferred.then(function () {
-				// try to acquire the session
+			deferred = deferred.then(dojo.hitch(this, function () {
 				okButton.set('disabled', true);
-				return umc.tools.umcpCommand('computerroom/room/acquire', {
-					school: vals.school,
-					room: vals.room
-				});
-			}).then(dojo.hitch(this, function(response) {
-				okButton.set('disabled', false);
-				if ( response.result.success === false ) {
-					// we could not acquire the room
-					if ( response.result.message == 'ALREADY_LOCKED' ) {
-						umc.dialog.alert(this._('Failed to open a new session for the room.'));
-					} else if ( response.result.message == 'EMPTY_ROOM' ) {
-						umc.dialog.alert( this._( 'The room is empty or the computers are not configured correctly. Please select another room.' ) );
-					}
-					return;
-				}
-				this._currentRoom = vals.room;
-				this._currentSchool = vals.school;
-
-				// reload the grid
-				this.queryRoom();
-
-				// update the header text containing the room
-				this._updateHeader(vals.room);
-				this._grid._updateFooterContent();
-
+				return this._acquireRoom(vals.school, vals.room);
+			})).then(dojo.hitch(this, function() {
 				// destroy the dialog
+				okButton.set('disabled', false);
 				_cleanup();
 			}), function() {
 				// catch error that has been thrown to cancel chain
@@ -773,9 +782,11 @@
 	},
 
 	_updateRoom: function() {
-		this.umcpCommand( 'computerroom/update' ).then( dojo.hitch( this, function( response ) {
+		this.umcpCommand( 'computerroom/update', {}, false ).then( dojo.hitch( this, function( response ) {
 			var demo = false, demo_server = null, demo_user = null, demo_systems = 0;
 
+			this._nUpdateFailures = 0; // update was successful
+
 			if (response.result.locked) {
 				// somebody stole our session...
 				// break the update loop, prompt a message and ask for choosing a new room
@@ -855,6 +866,27 @@
 				systems: demo_systems
 			};
 
+		} ), dojo.hitch(this, function(err) {
+			// error case, update went wrong, try to reinitiate the computer room (see Bug #27202)
+			console.log('WARN: the command \'computerroom/update\' failed:', err);
+			this._nUpdateFailures++;
+			if (this._nUpdateFailures < 5 && this._currentSchool && this._currentRoom) {
+				// try several times to reconnect and then give up
+				this._acquireRoom(this._currentSchool, this._currentRoom, false).then(function() {
+					// success :) .... nothing needs to be done as _acquireRoom() takes care of anything
+				}, dojo.hitch(this, function() {
+					// failure :( ... try again after some idle time
+					this._updateTimer = window.setTimeout( dojo.hitch( this, '_updateRoom', {} ), 1000 * this._nUpdateFailures );
+				}));
+			}
+			else {
+				// fall back, automatic reinitialization failed, show initial dialog to choose a room
+				this._nUpdateFailures = 0;
+				this._currentSchool = 0;
+				this._currentRoom = 0;
+				this.changeRoom();
+				umc.dialog.alert(this._('Lost the connection to the computer room. Please try to reopen the computer room.'));
+			}
 		} ) );
 	}
 });