Here is a quick fix for the Android Market after following the instructions on the front page of this thread and you get the error when running the market app after rebooting after the fix and so you don't have to constantly reboot and hope for best.
Go to settings and then click on accounts&sync settings and now un tick background data and now go back to the home screen and run the Android Market application again and it will tell you that it needs this and enable it via the button to the left.
Now you may get a couple of server errors but keep trying and it will work