So, slight problem, using cgminer w/2x6870's.

After finding a block yesterday, I've had nothing but 100% rejection rate all day.

[2011-08-27 09:30:14] New block detected on network, waiting on fresh work
[2011-08-27 09:30:16] Rejected 348df813 GPU 0 thread 2
[2011-08-27 09:30:32] Rejected e31cc19b GPU 0 thread 0
[2011-08-27 09:31:35] New block detected on network, waiting on fresh work

So on, so forth, anyone have any idea what could be happening here?