There are some scattered reports out there of nouveau producing this EQ overflow
I've used nouveau with many other cards and I had never seen it happening.
Maybe it has to do with this particular card I'm using now.
However, this freezing of X was not necessarily assocciated with having two cards
, but with this problem between the nouveau driver and my card.
In this case (although I usually prefer not to) I replaced the open source driver with the proprietary Nvidia driver, and I stopped having the problem. All is running smoothly as usual now
Thanks a lot for the input on this.