T61P cannot turnoff LCD backlight by power manager (Update)

[bomix_chan]

First want to say sorry that it may be a stupid question.

My T61P had set to turn off the display after 1 minutes, sometime it don't work after the time go. But it will be ok if I restart it. If I do nothing, it will still keep on work. But if I use seamonkey and/or IE and/or some other program, plug in power adapter, unplug some hardware etc, in most time it cannot work again. I had try set the screen saver start at same time, later or earlier than the turn off time at power manager. If it cannot turn off the backlight, it cannot go to sleep or hibration too. It didn't happened in my t23 before. Any ideal??

Please advise. And Thanks.

[bomix_chan]

Update.

I had try programs, and discovered if I don't start IE, seamonkey is work fine. I can edit all power manager setting and seen work too. but if i start IE, backlight off and suspend is non-function. Any ideal? my IE setting?? as my personal like seamonkey more, but company need me use IE, any advise I can try to solve it?? Many thanks.

Upupdate:

ok, after days of working, discovered seamonkey also sometime will diactive the autooff lcd function, logoff and login again will solve the problem, but if it start the browser again, surf around, it turn off again, if I don't start the browser again, it work, so I think it shoud not be a hardware problem

It work fine again once but it back to worst again after it restart. Still no ideal what's going wrong. Any suggestion?? Many thanks.