Well a number of people have posted their scripts, look at the Hardware Comparison Charts to see what flags people ran via certain cards and software.
If anything, just delete the current cgminer.conf you have and then restart. And check that you have the latest proprietary drivers installed in Ubuntu. They have been better about getting AMD Radeon updates.
I tried it all. I used many configuration flags, but cgminer always stops. On Windows all work fine. On ubuntu i tried use the same configuration, but it still stops.
On ubuntu i installed DiabloMiner and it works fine, but only with one GPU..
2Moderator, can you please move my thread to "Mining" forum?