[Trygon]

This problem was bugging the hell out of me... Pretty much all the symptoms have been listed already. Upgraded to 6.5, problem started, hard reset, problem went away for a day or two, then came back, no combination of .cabs or settings would fix it.

I noticed that my Yahoo email was not working most of the time on my phone. I would occasionally get crash reports for tmail.exe, and I only recieved emails every few days. On a hunch, I deleted my email account from the phone. Since then, my backlight button has performed flawlessly. Note that 'since then' constitutes about eight hours. I don't know if the phone hates Yahoo, non-outlook mail, email in general, or if I'm going in the completely wrong direction, but being as nobody else has floated a solution yet, I figured I'd throw in my two cents.

I hope this works - This issue is the only problem I have with an otherwise flawless phone.