Quote from: MickeyT2008 on May 18, 2013, 09:37:52 PM

Quote from: MyOldGeForce on May 18, 2013, 08:49:23 PM

Quote from: kanta on May 18, 2013, 09:17:39 AM

I believe this is the workaround (pics and all in there to make it easy)

http://bitclockers.com/forums/index.php?topic=7.0

Then that isn't the problem. I measured the corresponding pins on the monitor when it was unplugged, I got about 80 ohms.

Now I have tried running only a 4870 and also only the 4850 that worked before. Now they don't. Driver: 13-1 legacy. I'm beginning to think something in Windows is corrupted. For speed reasons, we deactivated windows update when we installed this machine, and then forgot about it. Now I have re-activated it to see if that does the trick. It will take some time, so I'll try it tomorrow. It's 10:50PM here in Sweden.

Have you tried using one of the older full Catalyst Suite drivers that support the HD4xxx cards as opposed to the legacy drivers? (not available for Windows 8 ). The legacy driver set doesn't support hardware accelerated OpenGL support, (no Minecraft Cry

) so perhaps OpenCL is compromised or removed too.

Yes I have. The legacy driver set for Windows 7 supports OpenCL, it even worked before I tried using two cards.

Quote from: MSO on May 19, 2013, 12:47:16 PM

Quote from: MyOldGeForce on May 12, 2013, 09:31:54 AM

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?

This happened to me when I upgraded Catalyst from 3.1 to 3.4 using only a single card (7770). Catalyst 3.4 fixed some display problems (flickering pixels) but slowed my miner around 20%. I wanted to revert back to 3.1 so I uninstalled all AMD software (including the driver via device manager) and then installed Catalyst 3.1. GUIMiner failed to start after this with no error message.

I can only speculate, but I believe that the OpenCL package is not removed when Catalyst is uninstalled. Software developers frequently leave support packages, such as OpenCL in place because they cannot determine if other software not written by them may be using the interface.

So when the older reinstalled Catalyst 3.1 attempts to use the newer OpenCL from Catalyst 3.4, its probably misusing a changed interface causing an error that GUIMiner doesn't know how to handle.

Thanks! Could Windows' system restore function help? I think I'll try that.