both are running at 895 MHz...yet the replacement still hashes at half rate

Hi,


I had 2 x 5870, non crossfire hashing 374 mhashes each 24/7. one broke and i got a new one.
the new 5870 is mining at 166 mhashes, while the other (old) is mining at 374 mhashes.

anyone experience this as well ? is the new card broken (shaders fried) or would it be network lag or issues in the pool ?

best regards
bubba