Originally Posted by MontyJ
Win8 and SSD's are a possible common link to the problem. The fact that the 64bit version crashes in Safe Mode pretty much eliminates rogue program drivers, etc. I did try to run the debug mode on Calibre in Safe Mode, but it produced no entries at all.
You might want to try backing up calibre's configuration folder (unsure where it is located on Win 8. Once it is backed up delete or rename the original folder. Then start calibre it will create a fresh configuration folder on start up. If the problem is in this folder you should be back up and running. Albiet you will have to recreate your settings and add in your plugins again.