What about W7 HP SP1 64-bit and Mozilla Firefox 12.x (with FlashGot add-on). Doesn't seem to do the trick for me anymore (and neither does the release candidate...).
Don't know what I did differently, but I tried FDM again (for the tenth time or so) and now it seems to work. Perhaps it was HTTPS that was unchecked or it looked like the site manager "forgot" my settings. I also saw settings like "r12345.rapidshare.com" instead of "rapidshare.com" in site manager or settings that disappeared after I closed and opened FDM.
A bug in FDM or gremlins perhaps? Lets hope it keeps working this time...