I just thought of something, because something similar was happening to me a long time back, but I can't for the life of me remember what I did to fix.
However, one o the procedures which stirs som grey matter is something about favicon.ico - when you bookmark a page, if that page uses a favicon, the bookmark will always try to load that favicon to display in the bookmarks menu, continuously.
http://www.aignes.com/deadlink_history.htm
I used that to remove all dead links in my bookmarks (can't be sure it was that exact thing, but it did the trick to track down dead bookmarks.
Please try that route, as I can't remember anything else working, but I know that removed lots of dead bookmarks, and the next memory of the situation is I had no more crashing probs.
Sorry this is vague, but hey, I know I have have lots of disconnected neurons....but it may help