well assuming it isn't just one of those things, have you tried a full uninstall of everything (option from add/remove of driver), delete the two dll's then install again?
for scrypt with cgminer, catalyst 12.4 with sdk 2.6 works well
I went further than that
Uninstall all ati (was on 13.4 at that time)
reboot
remove opencl (via the opencl.msi package from the 13.1, which I tried to add)
reboot
remove files in syswow64 & system32 (opencl, atiocl ... clinfo, all that, based on date) and ati/amd folders in program files / program files x86
reboot
reinstall 13.1 with setup
reboot
tried diablominer. success !!
I tried 13.5b2 before, same result but it was expected as opencl driver is the same that in 13.4
So now I'm back with working 13.1
The best I managed to obtain with 13.4 (even tried to install 2.8 sdk) was 100% hwerror :/
Damn, they really f*cked up everything with those catalyst. Why the hell did they want to integrate opencl into the driver itself ?!