Changed video to Radeon 5700 Series and found that our application produce VPU recovering if I run it twice. We use Catalyst 10.2 and Windows XP, CPU is i7 920.
During investigation we found that the problem is in GetRenderTargetData that is called from different processes twice. I created interprocess synchronization object to synchronize GetRenderTargetData calls between two and more processes and look like it works stable right now.
I'm not sure that this is good solution, because if some another application will use GetRenderTargetData at the same time and we will have VPU recover. I think that this is problem (deadlock) should be fixed on driver level.
Also no problem was with Radeon 4800.