Yes, I am having the exact same problems you are having. I Googled it and someone said if you download their "tool bar" available on megaupload site, that it fixes the problem. I have been messing around with it for about 5 minutes and I have yet to see what it is all about.
Heh... we're on the same path it seems. We've probably seen a lot of the same forums already.
I just signed up for OpenDNS (on a suggestion on one forum) to change my DNS server, but now I'm wishing I hadn't since that did nothing to fix my problem.
I've rebooted the PC countless times, I've reset the modem and the router. I'm constantly deleting the megaupload cookie, and I've even tried with all antivirus/firewall stuff turned off.
Now when I am uploading to megaupload, after the 15 seconds it takes to upload a 317MB file, it not only locks up firefox on me, but whenever I try to load the Task Manager it errors out on me. A reboot of the computer allows me to use Firefox and the Task Manager again.
This is bullshit.
Sorry everyone, but I don't think I'll be releasing any teasers. I've already wasted over a day on this crap.