for scrypt with cgminer, catalyst 12.4 with sdk 2.6 works well
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 ?!