I am stumped. please help!

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hey guys. I am having problems with an Inspiron 7500 on a docking station. the problem is when the end user tries to run an mpeg while docked it shows the first frame then it goes blank. the sound continues to play though. It does work fine when the machine is not docked. I have already updated driver for the video card, monitor, changed refresh rate, disabled pci steering, and same problems.
Another thing that I noticed is that it will play files that are maybe about 1 meg big fine. it will not work if the file is larger than 2 megs.

please help!!!
video adapter is an ATI rage Mobility card w/ 8 mb
thanks.

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hey its me again!

beleive it or not, if you have the wrong monitor specified it can cause problems some times, the minimize buttons, restore button and close button on the uper right hand of my montor were 100% black til i specified a non- plug n play monitor