How long have you had your bb? Who is your carrier?
I got my tour from sprint about two weeks ago. It did the same thing. Took it back the very next day, after extensive google searches for the problem. Sprint rep tells me its a minor glitch they are seeing in <10 of bbs, hence the reason for not finding it on google. They instantly replaced my bb with a new one, no problems since. Another thing you may consider is trying to install the new OS (if available). This may or may not fix the problem. Sprint does not know if it is software or hardware related.
There's been a rash of memory problems lately, if you search through the forums you'll come up with a bunch of stuff on this. Try pulling the card and see if you still have trouble.
The file system on your memory card is easily corrupted. If the BB does fine with the card pulled, move your files off the card and then format the card in the BB. Move your files back to the card.
But then again, 1 GB? Are you kidding? lol. Memory cards are cheap now, buy at least a 4GB card and install that.
In my experience, the phone rebooting was more like a computer crashing. I find that FB used a lot of free memory (RAM). Add that to all the apps, possibly, running in the background, and you'll quickly find yourself waiting for your phone to reboot.