N03L and Others,
I think it might be a bit too late for you as you most likely blew away your databases but hopefully this will help others. I was having the same issue of the synchronization service not starting after being unprovisioned. I was reading this article to see what might be the problem and I came across this section:
"Firstly, you must run the UPS Service Instance as the Farm Account. Just because its possible to change the service identity in Manage Service Accounts, doesn’t mean it will work, and more importantly it is unsupported. So don’t change it.
Next, the Farm Account must be a local administrator of the machine running the UPS Service Instance during provisioning only. When we hit Start in Services in Server a series of tasks are run, which are akin to running the second stage of the Forefront Identity Manager setup. Many of these tasks require local machine administrator rights. You must grant this right before hitting start, and more importantly they must be applied. As the Farm Account is running services on your box (SPTimerV4 and the Central Admin app pool) we must simulate a log off and log on for the change in rights to be applied. You can do this by restarting SPTimerV4, or better yet, rebooting the machine. Once UPS is provisioned you can remove the Farm Account from the local administrators group."
Because we have had problems in the past with the UPSS I tend to watch as the service is being provisioned to watch it set the service accounts, startup type and then start the services. This time I noticed it was trying to start the FIM sync service as the synchronization account and not the farm admin, this made me go check settings. It turns out that SharePoint changed the manage service account entry to our sync account. I have a feeling there is some bug in the UPS provision process that checks for synchronization connections and if there is one it changes the UPSS managed account to the account used there instead of the farm account. Which according to the above is a no-no. I am about a year behind on my blogging but if I get a chance i'll write this up on mine in more details.