I don't know if any of you are still monitoring this thread, but I was having the same issues, and went through all the same chores that you did and more on top of it. It turned out to be something very simple that is known by some members of the community. The answer for almost all of us having this issue was to Turn off ULPS in registry.
This issue was driving me nuts, but I found this fix and it worked, and it seems that it worked for a good number of others too. This is something AMD really, really should (and could) fix. But we can manually fix it, even though it can be a pain to do so (the biggest pain was trying a hundred different things before finding this info).
Here we go:
1) Click Start - Type regedit.exe, right click on it and select to run as Administrator.
2) Back up your registry in case you make a mistake. Click on File, then Export, and save a copy of the registry somewhere.
3) In the registry editor, press F3 and type EnableULPS, hit enter.
4) It probably will find this as the first search entry in a sub folder 0000. Make sure the value is only "EnableUlps" and nothing more (NOT EnableUlps_NA).
5) Double click the registry entry for EnableUlps and change value from 1 to 0.
6) Again, do not touch anything else, such as the related file named EnableUlps_NA
7) Continue to press F3 and look to see the EnableUlps file in the other numbered folders (0001, 0002, and so on - for my card it went up to 0006). It will probably already be 0 in the other numbered folders, but in case it's not, if it is 1 in any of those, double click the registry entry and change them from 1 to 0 in the other numbered folders as well.
Continue to press F3 and you will also see the same entry in a Driver subfolder (EnableUlps). Double click on it and set it from 1 to 0 wherever you find the specific entry.
9) If this fixed your situation, do a little happy dance, as this horribly annoying issue is finally done and over with!
10) Save these instructions for the future. When you update your Drivers or have to do system rollbacks etc, it may come back, and you may need to disable this function again. It also is almost always the cause of this horrible issue, and we need to make sure to pass it around to other AMD users.
In case you're worried that this is disabling something important, it's not. ULPS stands for Ultra Low Power Setting. It's this ultra low power mode, unrelated to your usual power settings. If it sees that your monitor is switched off for a little bit, it turns itself on. And yet for some stupid reason, it doesn't turn itself back off when you turn your monitor back on or try to use your PC. So it's in this ultra low power mode that can't even send a picture to your monitor, and for a great many of our systems, it doesn't know enough to toggle back out of it unless we manually reboot (or worse - unplug for some people). So it's nearly useless, causes all sorts of issues, and you don't have to worry that you're turning off something important.
