The "invalid share" issue has been fixed!  Please update your miners.

In addition, you power users might want to check out the "-s" flag.  It lets you specify the GPU load per hash pass.
It multiplies the work load by 2^X, so "-s 1" does twice the work, "-s 2" does four times the work, and "-s -1" does half the work, etc.

For more information, run the miner without any parameters.  The help screen will tell you more.