Some months ago my Firefox got flaky. Screens showed in odd colors, or just black and white. Some buttons (reply) on some websites stopped working. Printing became erratic or came out in strange colors.
Fix. Create a brand new user account and use Firefox from the new account. All the colors came back, the invisible buttons re appeared and print worked right.
Of course I had to re apply all the fixes I had to apply to Windows XP to get the new account to look right. (show classic start menu, show classic Explorer, and more).
Why does this work? Windows must store some customization information in each user account ("loading your personal settings") which gets corrupted and cannot be fixed. It is NOT a firefox problem per se. I executed the procedure to refresh firefox's "profile" (private, per user status file in which things like passwords and bookmarks are stored). No luck. I had to create a whole new Windows user account and then do the Firefox "create new profile" bit in the new account.
I love Windows.
PS. It rained on the newly stained deck today. The water beaded up nicely on the new stain.