It's funny, because I've had a laptop in almost the same model, with an almost identical problem.
Video works fine until the GUI starts to load, at which point the video just craps out.
So, there are two possible solutions I've found, and unfortunately both of them require you have access to another Mac.
The first solution is to put your MBP into target disk mode, and then using another Mac, boot the OS on your MBP's HDD. IIRC, and I've never tested it with USB, target disk mode requires a FireWire 400 or 800 connection to work. This will reset the resolution in the OS preference files, and so when you shut both systems down and reboot yours, it SHOULD work. However, on the system I was dealing with, that only lasted for 1-2 boots. Not sure why.
The other solution, credit goes to one of Apple's support people for coming up with this one. You again need to boot in target disk mode, and then delete the following files:
~/Library/Preferences/com.apple.systempreferences.plist
Displays preferences
(never found this one, so not entirely sure where it's supposed to be)
~/Library/Preferences/ByHost/com.apple.preference.XXXXX.plist
~/Library/Preferences/ByHost/com.apple.windowserver.XXXXX.plist
and anything dealing with it in the /Library
Then reboot and clear the PRAM just for good measure. And ~/ is Unix speak for your user directory. So /Users/{YourUserName}/Library/
In my testing that last one lasted for at least 5 boots in a row. A month or two later the person sent the system back in for the same problem, but my job is fixing broken hardware, I only tend to do software issues when they either intrigue me and I have time or I figure I can solve it in under 10 minutes.
Ultimately, some program or device that is causing your display preferences to become corrupted. I have no idea what it may be, so you're on your own there unless someone here has some ideas. My guess, based on the one time I've run into this issue before, is that nothing short of an OS reinstall is going to permanently fix it.
<span id="INSERTION_MARKER"><span id="INSERTION_MARKER">Macbook Pro boots up and video display get stuck on apple logo with grey background, the OS continues to load and I can hear ichat login. I can see the share drives over network, and can send chat to it, and hear the chat alert, but video won't display the desktop, it just show the apple logo boot up screen only. I tried zapping PRAM (CMD+OPT+P+R) and reseating the RAM. It always boot up and get video get stuck at the logo. This is a MPB 15" 2008 (non-unibody). I think my Apple care just ran out. Please help.

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