From the screenshots, it looks like Trixx just sets the voltage, but doesn't read it. You can set the voltage in Afterburner just fine, the problem is when you have muliple programs reading the voltage. So in Afterburner I have found it's safe to "Unlock voltage control" but if you have another monitoring program you should not run "Unlock voltage monitoring".
Besides, I didn't even have GPU-Z running when it happened to me, the two programs conflicting were Everest and Afterburner...
Edited by Kick - 3/6/11 at 7:15pm