I am having a strange issue.

I am unable to adjust the clockspeed on my miner if I set it to anything other than 800 it fails to hash anything and stops responding
here are my settings
bfgminer.exe --scrypt -o stratum+tcp://poolurl.com:4224 -u bla.user -p password --no-longpoll -S MLD:\\.\COM5 --set MLD:clock=800 --verbose

This seems to be the only setting that works, If I set it higher, or lower it fails to respond. 800 is not even in your list of preset clock speeds. I've adjusted the power, lowered it, raised it, not difference. It is hashing at about 3.4Mh/s with HW:251/.20% in the last 21hrs.