Very very annoying error, I know. This is one of those errors that Microsoft decided not to provide a lot of detail. I just spent the better part of 2 hours searching the web trying to find a solution. I found a lot of differing fixes, but none seemingly applied to me. I finally sucked it up and applied each solution I found even though "I know that's not the issue." Silly me.

I had this occuring on two servers at the same time, a customer server and my development server. The issue with my development server is that we recently moved our servers to a new domain and ran all of the stsadm commands to update the farm to the new domain accounts. It appears that even though you run through all of this, you still need to go to Central Admin and update the service accounts. Thanks http://blog.ozippy.com/2008/02/sharepoint-2007-workflow-on-start.html. That fixed my development server.

My customer server wasn't so easy. I wasn't getting anything in the logs that was useful. The server never switched domains and the workflow had been running great for quite some time. I recent reviewed the entire workflow and added error handling where some was missing. I must've accidently changed the token in the workflow. Seeing article http://www.sharepointassist.com/2009/09/09/workflow-failed-on-start-retrying-again/ I decided to take a look at the CorrelationToken. It looked ok, but I went ahead and renamed it and set the OwnerActivityName to the name fo the workflow. Rebuilt the WSP and deployed it and it worked great! Why did it work fine on my dev and not my customer server? I have no idea.

If these solutions don't help, check out the logs. Search for your workflow name or just "workflow", you might see something like "Engine RunWorkflow: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation." If you continue reading this line, you'll see what's causing the issue.