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...

This issue can be caused by the McAfee SiteAdvisor or BlackSheep extension (Tools > Add-ons > Extensions).

solved it when i disabled mcafee site adv

I still can't get any more than 4 of my bookmark folders offered at any time.

i have to create a new folder to see the full list and then delete the new Folder so that I don't acquire a hundred of them over time.

It seems to be hard-coded in the current FF - any way around this?

Make sure that you click the second arrow at the far right of the Folder line to open the full folder list. In the other smaller list you can click the "Choose..." item to get the full list. If folder in the full list aren't open then click the + at the left.

You may also need to check http://kb.mozillazine.org/Corrupt_localstore.rdf

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems