Nightly Tester Tools would not make PWM compatible with PWM; I had to download and reinstall the Add-on Compatibility Reporter extension to get PWM to work with FF 8.
(Later) I just had reason to open PWM and change an account. When I right-clicked on the account, the pop-up menu was almost unreadable. I have not tested this with the default theme, etc., so I'm only reporting what I have found so far.
(Days Later) I just created a new account; it took me a short while to realize that the previously-unreadable pop-up menu is now restored to a readable condition. I have not the slightest idea as to what caused this change, given that I've not changed anything in Firefox, as far as I can recall (which is, of course, at least 1.56 minutes...) that might have affected PWM.
(Later still) Now the problem has returned. Quite strange, and I really don't want to create yet another new profile, sigh.