@kalroth i do not like to prove you wrong

i have two pc's nearly the same
both with windows 7/64bit (one ultimate/one professional) two different mainboards
but on both pc's i am using two His hd7850 with the same settings.
(using sgminer 3.7.3 -->much more stable and better finetunable to xintensity....)

pc 1   i do not use queue, scan-time and expiry (so defaults will be used afaik)
pc 2   i use queue=0 scan-time 1 expiry 1

So quess what after 18 h of mining

pc 1 786,57 Mh/s Wu:685  Rejects 9,5% --->problem cards or pc or settings ?
pc 2 785,13 Mh/s Wu:746  Rejects 4,7%

so i swapped both cards from one pc to the other one and let settings as they are.
Test for a night (10h)

pc 1 has again the lower WU: and the higher rejects (7,1% to 3.7%) ---> so no problem with the cards, maybee problem with pc or setting ?

(to be honest is was the night where cleverming has ddos attacks and both pc's stay several hours at middlecoin
maybee therefore both pc's with lower rejects ?)

before driving to work i just switch the configuration and at the end of the working day (10h)

pc 2 has now the lower Wu: and higher rejects (4,9% to 10,1%) ----> no problems with the pc it should be the configuration?!

i double check both configuration and the only difference were the values (scan-time/queue/expiry)

This weekend i will move all 4 cards to a selfmade rig..... next test will be monday

stay tuned

@kalroth will there be further improvements for 3.7.3 or is sgminer to be prefered for the future?