Cool. Great thing for guiminer users, then. Never tried mixed hardware using it. I do know it is an issue with others - like cgminer or bfgminer. I pretty much use cgminer exclusively these days.
No problem with CG... You can even use best SDK and driver combination for every card...
Thanks for all the answers
I know my forum name is confusing. I began with an old GeForce card, but I have a friend who works with computers, and I have borrowed other cards from him. Currently, I am running one AMD Radeon HD 6700 series.
The driver is version 12.104.0.0, from the 13-4 installer. I have been switching drivers back and forth because I have been trying to mine on that card simultaneously with a 4850. No matter what I do, I couldn't get that to work, GUIMiner didn't start, it only got a tray icon that soon disappeared. With some drivers other programs crashed. As I said, I have spent at least six hours and twenty reboots on (not) getting it to work. I think I got all other drivers out before installing the one I just mentioned.
I think the problem lies in the drivers, if you search AMD.com, you will find that a 4000 series card don't use the same drivers as 6000 series card.
Mixing 5000, 6000, 7000 cards is ok because they use the same drivers.
I have tried to install different drivers for the cards, and I have tried installing a previous version that supports both cards. Neither worked. It seems to be the combination of the new card and anything but the new driver that makes GUIMiner not start.
Now, when I am running only the new card, Phoenix and Stratum Proxy, it stopped working tonight, a few hours after I started it. I restarted the miner this morning and it worked again. I hope it's a one time occurance, but I doubt it. It didn't happen with Phoenix and BCPool. Any guesses?
My estimsted rewards seem to be about right. I'm not exactly sure what they should be, but they are not in the 7 satoshi order of magnitude... Currently it's 0.00051612 and I've been running 200 MHash/s for 1.5 hours.