I've not had that problem. On my desktop, Gmail works perfectly all the time. On my laptop, it tends to freeze up and it will unfreeze itself after a long delay. If I try to get out of it, I get that "the program is not responding" message. I think that must be some sort of Windows issue.
On my dinosaur computer, sometimes Gmail freezes up, but I haven't had any real problems with Gmail itself. I just close the window and start all over. I love Gmail more than any other one that I have ever used.