Do you have that problem when running in the Firefox SafeMode?
http://support.mozilla.com/en-US/kb/Safe+Mode
Don't select anything right now, just use "Continue in SafeMode."

If not, see this:
http://support.mozilla.com/en-US/kb/troubleshooting+extensions+and+theme...

Ok, I've never tried safe mode before, so I just tried it on your advice, my form history displayed! Now what? I have no idea which extension, theme etc. might be causing the problem..

I just looked at the second link you provided and decided to try to reset toolbars and controls and my form history worked again! I then tried switching back to the theme I was currently using and the problem resurfaced. So I guess I know now it was the certain theme that was causing it. Thank you so much for your help!! Any idea what I can do to stop my form history from deleting after I leave Firefox idle for more than 5 minutes?

Well, I wrote too soon, my form history is still problematic when I exit Firefox and go back in even with the default theme. I guess I have to keep trying to figure out what is causing the problem.

I don't have many extensions so I decided to disable them one by one, and it looks like it's my google toolbar. Will uninstalling and re-installing it help?

Yep, this is def a problem with the google toolbar. I did find that if you turn off the google autofill, you can keep the toolbar enabled and the problem goes away. The browser then uses Firefox's autofill instead. Thanks for leading me down the right track. I didn't want to lose Google toolbar, but not having form history has been a pain, since i use it for shipping packages and not having it makes it time consuming.

Hi all,

I am having the same annoying problem.

I just disabled the autofill option in the Google Toolbar, and sure enough, my form history appears to be working again!

It's too bad... I liked the autofill feature for my addresses and so forth.

Any further resolution on this? The google support site isn't great...