Freezing upon quitting both Sgminer and Cgminer

Hiya

Im on Xubuntu 12.04.02 With Catalyst 13.12, No SDK (as Ive understood its unnecessary on linux?), Cgminer 3.7.2 and Sgminer 4.0 - Harware config is a gigabyte Ud5 Mb, Amd fx 8 core CPU, 3 x HD7950 Sapphire radeons (have two more but only running three until this problem gets sorted), and 2 x corsair RM750's.

I have had stability issues from the beginning and have had to do a number of hard resets, due to system freezes. The system freezing whilst in the process of mining was resolved by adding more ram. Now Im running 2x2 and 2x4 (12 total).

When I run Cgminer or Sgminer, the system does fine until I try and quit. When leaving either, after I hit the Q command, the system locks and I have to go into soft reset. Initially I had thought this was a glitch with Cgminer and Linux, so I tried to install Sgminer, thinking that since Cgminer hasnt been updated for such a long time (for scrypt) that it would be a problem that had been resolved in SG. The other freeze factor is once my monitor falls asleep, when I wake it the system also freezes. Everytime it been running for over 5 minutes this occurs. Within a 3-5 minute window, however, Im still able to quite either of the programs without freeze, and after hitting q, Im taken back to the command line directory where I chose ./cgminer.sh.

Ive done substantial research trying to figure out a number of combinations that have caused this - I was previously on Ubuntu, now Xubuntu, from Cg to Sg, etc. Also have messed with the config file, and if Im extremely low on the intensity, it also doesnt happen in either - but these are pitiful hashrates of 300, or along those lines, and highly unacceptable for 7950s.

Hopefully someone has had similar experiences and can shed some light?

THANKSSS!