That sounds a bit like what I had recently. The CMS stops working in mid-flight, stops just as DS starts (just after splash screen clears).
I got round it by simple expedient of, with the CMS stopped, copying the CMS database directory, then deleting the original database files. Restarting the CMS should repopulate with basic files, then you can process metadata and import metadata from the DB maintenance pop-up menu in the content library.
As an aside I also tried to reset database first (before deleting the files) but something went a little wrong, I think, and the process ground to a halt after it had eaten up the remaining 25GB or so of my hard disk ... 