I have exacly the same problem... at the beginning, just after installing v2 everything was fine... it started after few hours of v2 usage (tests, adding/deleting galleries, changing/saving setup options etc)
In folder names i used some special characters like [ ] or ( ) for examle "[2008.07.23] My gallery title"... I'm not sure if this is a solution but after deleting this special characters i have no more restarts... I will continue my v2 tests and let you know if restarts appear again...
its to do with the thumbnails - when I try to view a gallery that has timed out after trying to re-create thumbnails, it does the same - shows one or two quickly and then restarts the entire gallery engine...