-- Are there any yellow question marks or exclamation points when you open Device Manager? If so, make sure you install the drivers.
-- Check your video card temps, you may need better ariflow in the case.
-- If you have OCed your 5850, try using reducing to stock.
It could be that your are having a problem with overheating. Due to you using a crossfire setup I would check to make sure that your cards arn't running to hot. Also, have you tried running games, do you get artifacts during gaming, or just on the desktop.
Note: I was unable to open the links and therefore had to make some assumptions.
Other options are to try a different mouse if possible to determine if it is a card problem or a mouse issue. If there are still probems with a different mice then you may have a graphics card driver issue. Try reinstalling the drivers, and if that doesn't work try a different version of driviers. I found 10.4 to work the best for my Crossfire setup. What version of drivers are you currently using?
I got it while playing sc2. When I exit the game its still there but when restart my pc its back to normal. My temps went as high as 70 while playing. All the settings are on stock. My rig looks like this by the way.
I'm pretty sure it's more of a windows thing, and you mention it happens after SC2, which is something I also get from that game. Never, ever happens elsewhere. SC2 does something funny lol. I don't think it's really related to the cards.
You can definitely over clock them. Get MSI Afterburner, and in it's config file change "unofficial overclocking = 0" to "= 1" then you should be good to try overclocking.
Of course you don't have to. Like I said that was a pretty good score. But the only way to increase it is overclocking. The question is, do you notice your framerates are lower than you'd expect in the games you play? I decided to overclock my reference model Sapphire 5850s, I run them at 870/1200 all the time and if I really want I have a profile for 985/1210 for benchmarks.
Vapor X cards only give a small overclock at stock... it's really nothing much. IMO their main advantage is the good cooling so that you have a higher thermal overhead for overclocking. I can't run FurMark with 985/1210 because my temps will get too hot, but in games and benchmarks they stay reasonable.
And did you change the config file? If you didn't, it will be limited to the same max as in CCC's ATI Overdrive.
ATI cards don't have shader clocks.
Voltage apparently is locked, but you should still get at least 850 core and 1150-1250 memory clocks. Unfortunately you can't unlock voltage because it's a physical component on the PCB that regulates it.
You might be able to adjust it, I don't know if it works or not on locked voltage cards, by using RBE (Radeon Bios Editor). I used this to edit my 5850 BIOS many times, and doing this I flashed my cards so that their 3D clocks are 870/1200 but they still drop to 157/300 at idle (I'm hoping you noticed after you bumped your clocks in Afterburner that they idle at 400/900). Within the editor, I can manually adjust the voltages so that at 870/1200 it can use whatever I want - this would be handy if I wanted, say, 960/1200 I could just set the voltage to 1.18 or whatever it takes.
Anyway, editing the BIOS can be tricky so don't get into that unless you do a bit of research on it. RBE and the flashing tools, ATIFlash or ATIWinFlash, are both available from www.techpowerup.com along with tutorials.