I have an HP laptop. After I wake the computer from Standby, occassionally Internet Explorer or FireFox will freeze while loading a page. The only way to remedy this is by holding the power button for 5 seconds to force the computer off. I cannot exit the browser, and if I try to shut down or restart it will begin to close programs, but then it will not continue.
The standard answer is "microsoft is evil and must be destroyed."
Actually, I have an HP laptop, too, and if I let it go on standby, when it comes back it won't respond to the touchpad when I tap it, I actually have to click the button. That annoys me so much I reboot, so I haven't had your problems with freezing. I'd send email to HP customer service and see what they have to say.
Typically it is what thay call a software conflict, two or more activities are competing and this may freeze your screen. check your notification area in the lower right corner of your task bar and see what programs are there, some could be running in the background possibly causing the problem.