Your TC is too low. Minimum TC should be at 10240+. If i run anything under 10k i get HW errors.
I run my 10 270s @ TC 24k. You need to add that setx GPU_MAX_ALLOC_PERCENT 100 command.
Anything other than 8192 gives me error -61 and cgminer won't start. Even with the `setx GPU_MAX_ALLOC_PERCENT 100` added