Hello,
I am facing this exact same issue.
Deploying Windows Updates outside of the Task Sequence works perfectly, however when using the Build and Capture Task Sequence it hangs indefinitely with the status message "Downloading 30 of 30 Updates (100% Complete)..."
The last status message in UpdatesHandler.log is the same as yours: "Invalid Task State retruned"
For the ones wondering, no, that's not a typo.
Furthermore the status message "Waiting for job status notification..." keeps appearing in SMSTS.log.
I found the following article which applies to ConfigMgr 2007:
http://blogs.technet...-windows-7.aspx
Could it have something to do with this?
Did you manage to find a solution?
Update:
I've just found out that not only the Build and Capture Task Sequence has this problem, but the domain joined Install Task Sequence as well.
This should probably mean the problem does not have anything to do with the SLP or FSP.