Hi OP.
I wrote a detailed post on how I fixed the same problem on my setup which is almost the same as yours, only diff is I have 2 7950s & *Mb ram.
https://bitcointalksearch.org/topic/m.2152164I'm not sure which of the changes I made fixed the problem, but what I would try with your setup is this...
Open a new CMD window and run the setx commands. then close that window, you don't need to run that again. The setx commands do not affect the windows they are run in, only windows opened later.
http://www.tomshardware.com/forum/57485-45-setting-environment-variablessetx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
Move the .bat settings to a cgminer.conf file. The one I used is in my post I linked to. Try that.
You will need to specify 3 GPU values where I have used 2.
"thread-concurrency" : "14336,14336,14336"
Reboot & Start CGMiner
You could also try using CGMiner 3.1
Let us know how it goes.
thread shoud be a 64 multiple of the memory bit memory bus in the 7xxx series 384-bit 384 x 64 = 24576 , but i use 24000 or 21792.
I run 4GB with 4 cards 7950 - no problem I had 8GB pulled 4GB ZERO change .
i'd set you GPU engine to 1060 - then put your I - 19, see what you get?
also google "worksize" and "lookup gap" you should make a conf file.
all cards but the display run about 620k# with 74 Deg - display about 500.