Did you find an answer? is it related to the following: This problem occurs because a security fix in Windows SharePoint Services 3.0 SP1 prevents declarative workflows from starting automatically under the system account. Did you try the following:
The answer is pretty simple: install Infrastructure Update http://support.microsoft.com/kb/953749/(and of course if you are at it, you can update the
whole farm to the latest patch level (FEB CU) ) and pay close attention to one small line (made bigger here because of it’s importance) written in the notes part of the knowledgebase article:
To prevent the declarative workflows from impersonating the system account, the workflows will now impersonate the user who created the workflow association.
This basically means that you should create a special account not SHAREPOINT\SYSTEM, that is a site collection owner on the site collection where the workflow is hosted, open the workflow in SharePoint Designer while logged on
as this new account and simply save the workflow without modifying anything.
It will effectively change the account that associated the workflow, which will allow it to start.
Please provide feedback.