I'm not sure if this is the same problem or not, but when I log in for the first time after booting my computer, the monitor turns off. My laptop is plugged into a docking station and is always closed, and I need to open it until the built-in display comes on and then close it again. After that, my monitor works perfectly until I next reboot my computer. I don't have this problem when using the laptop as a laptop
Is your laptop connected to an external display? If so, does this work? If not, I'm sorry I couldn't be of more help. Please post more details regarding your setup and when this occurs.
I have an HP laptop running x64 windows, and the problem doesn't seem affected by service pack or Vista edition (although it doesn't happen under Windows 7 RC)
Edit: This is not the same problem; I just used the "Switch User" feature and it didn't help.