Bookmarks vanished

Short version of a long story. I share my computer with friends. Friend who only checks e-mail decided to check the long ranger weather forecast for the area. RealOne came up to show the weather map. Computer locked up tighter than .....well lets just say, it was not going to allow any further use. Finally mange to get things closed and down. When I re-opened my netscape browser, all........and I mean ALL the bookmarks were gone. I tried to do a online scan at panda, and appearently they do not offer that service anymore. I went to pcpitstop and ran the online virus scan and nothing showed up. Ran my own virus scan (panda) and she comes out clean.
Question: Would this be a worm, virus, or software glitch?

Any comments at this time would be appreciated. It's 8:35 p.m. eastern and I have to take off in 20 minutes, but tonight when I return, I hope someone will have answered that for me, as I really don't want to reformat.

Is there a reliable site I can test online for a virus?