I forgot to mention (i had actually forgotten completely) that I replaced the blower motor regulator a week or two ago. Come to think of it, this is when the troubles with the shutting off and locking up became constant (had happened a few times in the past).

I cheaped out on a $99 regulator on ebay, which was some sort of off-brand. Could this part be causing my problems?

Any help you guys can give will be much appreciated.