Try a newer or older version or reaper, or switch to cgminer and see how it works out.
I am really happy with cgminer on most mining, but will try reaper some more to see if i can milk out a few more hashes.
I've tried cgminer and I didn't like it + lower hashrate. And I believe I have the newest version of reaper... I have the same version on both rigs, and both of them are running the same exact settings, but that one keeps messing up for some reason.