I am using hardware version 4 for TrackIR.
I recently 'upgraded' to Windows 7... and while reinstalling everything I decided to try putting in software version 5. Now, while I was impressed with the new interface, I was less than impressed with how well it functioned using the new software. It would stick in certain angles like that... I would intermittently lost TrackIR functionality altogether from time to time during the game, and it seemed that when it DID work, the software was too busy trying to 'smooth things out' that everything seemed less precise no matter how much I tried adjusting and tweaking things. Also sometimes I would have to reload the software several times before I would get a green light on my camera. Very frustrating indeed.
I reverted back to software version 4 a few weeks ago and everything works flawlessly yet again. They claim that software 5 is compatible with hardware 4, but I don't think that's truly the case... at least not with Aces high.
Anyways.. if you're using software version 5, try downloading and installing version 4 instead (this is assuming you don't have hardware version 5). You shouldn't have to uninstall 5 for this.. you'll just have two instances of TrackIR software installed (you can then uninstall whichever one you want).