On my GUIminer its says I'm mining at 76.4 Mhash/s and it maintains that but sometimes goes ranges from 71.4- 76 but usually its maintains at 76.4 Mhash/s. When I check my account and go to the workers section its says that I'm mining at 47.306 Mhash/s. Is there something wrong with my setup? or is that how it is normally?
Try experimenting with different settings. I think the pools are calculating your mining power based on the number of shares you send. If you have too aggressive settings for your GPU, then you will just won't send the shares on time.
I have found that sometimes it can drop quite a bunch if I leave it running for a while. Not sure about the cause yet, but I've had my card at 21.7 mH (its slow I know).. and then leave it for a few hours and when I come back its done to like 5mH. Trying to find a solution. That may be destroying your averages though.
Check your Windows power settings. When I first started mining, my workers were stopping on each 30 minutes or so. Then I found that Windows is set to sleep if no activity. Silly me! I lost quite some time then. Just go to Control Panel -> Power check the advanced settings and remove any kind of HDD, VGA, PCI suspension and sleep/hibernate.
