I too am having an issue with the current beta. 4 minutes after Firefox starts with HMPA running, firefox locks up and I have to kill the process. Happens on several computers. Uninstalling HMPA fixes the issue. I will wait until the next beta, I suspect they will have it fixed by then. They have been taking some time off recently. Most like much deserved time off. Can you wait? We must remember this is a BETA product we are using. No guarentees.