That will be done tomorrow, only that and fresh windows install are the things that are not tried.
Fresh install and cross testings can't hurt indeed. Have you also tried solo mining for ETH with just
setx GPU_FORCE_64BIT_PTR 0
setx GPU_MAX_HEAP_SIZE 100
setx GPU_USE_SYNC_OBJECTS 1
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_SINGLE_ALLOC_PERCENT 100
EthDcrMiner64.exe -epool eu1.ethermine.org:4444 -ewal . -epsw x
Hope you find an answer. You could also try to switch pool for another one like dwarfpool just for testing.