I have had this problem since I installed the 2 HD 6970 right after the release, and it only occurs when chrunching VLAR workunits.
The workunits has between 0 and 1% CPU utilization, and overall CPU utilization is allways below 100%
Excample of lagging: if I hold down "a"-key on keyboard, it will take almost 2 seconds for the letter "a" being written into Notepad, and will only write in "hops". So even in the least resorce-hungry application for writing text the OpenCL processing is overpowering normal operations.
Windows 7 Ultimate x64 SP1, Catalyst 12.1, SDK 2.6.