SharePoint Workflows: Delay Activity not working/firing after GAC update

I recently had an issue with a Delay Activity not firing after I updated the GAC from Visual Studio 2008.

I finally found a MS KB that helped me:
"A workflow does not resume automatically when a delay activity is triggered in Windows SharePoint Services 3.0"
http://support.microsoft.com/kb/953630/en-us

Solution for my project: Restart the Service "Windows SharePoint Services Timer" after an update.

P.S. The same trick also helps to solve the "System.IO.FileNotFoundException" issue that can occur when installing a wsp with a feature receiver.