A strange thing: if i run my dual 280x right after login (win7x64) with -t 0,0,1,1 it runs fine with 7070 cpm and not "lagged" monitor at gpu 1. if i run cgminer (scrypt) before (and stop this of course), then i can not run at -t 0,0,1,1. Monitor gets heavy lag and mouse is not usable any more, very hard to close miner-window, cpm is down at ~4000. Problem is only the GPU with monitor attached, other one is fine, So i have to run with -t 0,0,1 (3 threads) only after scrypting. Maybe cgminer leaves a mess in gpu, maybe it´s a memory allocation problem in gpu-memory because of graphics? I´m a noob, but is it possible to init gpu (-memory) after start of your miner?

having a similiar problem here with Win7 64, R9 270x and 13.12 driver. if i start the miner directly after login i get 1350 cpm. If i start the miner after cgminer was launched and stoped i get around 560 cpm...i don´t care about that, but it might be interesting for other people testing and wondering about the low hash rate.