Maybe this is the problem of Microsoft Windows XP. YOu should try to contact Microsoft about this problem. Meanwhile, I am checking for this solution, and will report if I find any.

your useragent identifies your system as windows 2000 - this is probably part of the problem...

Thanks for your immediate answer -- I am amazed! ;-)

I saw the identification of my OS as W2000, thinking that this is odd and might be the problem. Only that I have no idea how this came -- and I never experienced any other problems in that respect ...

But my issue is (sort of) resolved anyway!

So far I always tried to either update from the "About Firefox" screen (resulting in "FFox is up to date") or to start the installer right from the download manager as I believed this just passes an opening/executing command for the relevant file to the OS. This is obviously not the case as I now tried starting the installer directly from Windows Explorer ... and everything went just fine! =8-)

The only remaining issue is the incorrect user agent string from within Firefox -- using http://thismachine.info I still end up w/ the following: "Mozilla/5.0 (Windows NT 5.0; rv:24.0) ..." which is resolved as Windows 2000. Why this happens I have no idea!

Doing the same from IE gave me (even before the install) "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; ...)" though, which is correctly identified as Windows XP. (Similarly in Chrome: "Mozilla/5.0 (Windows NT 5.1) ...".)

So I will probably have to keep on checking manually for updates in the future, but as XP is about to die soon anyway and give way for W7 this is not that big a problem.

Thanks again for your help -- you definitely pointed me in the right direction!

Cheers Jens

P.S.: I tried safe mode before, to no avail -- so it can't be one my extensions making Firefox believe or pretend to be from the Stone Age ... =;-)

hey, thanks for reporting back - it sounds a bit as if you're running firefox in compatibility mode for windows 2000: http://support.microsoft.com/kb/292533

That was it! I have no idea whatsoever how this happened (do you?!), but now I suppose it is fixed for good.

(I had found a hint in that regard at https://support.mozilla.org/de/questions/933214#answer-355147, but as this was pertaining to a different problem and I believed the installer to be the culprit I only checked the compatibility there ... =:-}

Thanks a lot again -- Best wishes

Jens