intensity for 280x should be set to 13
try deleting the shaders parameter to see if that fixes the HW issues
After deleting shaders, i still have got some hw errors.
Also I changed the intensity from 13 to 12 to 11, but every time i have harware errors.
Mining ultracoin with the following settings, without hw errors:
ultracoinminer -o stratum+tcp://ultra.nitro.org:3337 -u x.1 -p x --scrypt-jane --sj-nfmin 4 --sj-nfmax 30 --sj-time 1388361600 --thread-concurrency 16384 -g 2 -I 12 --lookup-gap 3 -w 256 --temp-cutoff 90 --temp-overheat 85 --gpu-powertune 20 --expiry 1 --queue 0 --no-submit-stale
And doge also with no hardware errors:
sgminer.exe -o stratum+tcp://eu.multipool.us:3352 -u x.1 -p x -I 13 --thread-concurrency 8192 -g 2 -w 256 --shaders 2048 --gpu-engine 1170 --gpu-memclock 1825 --temp-cutoff 87 --temp-target 77 --auto-fan
No luck this coin

with these settings:
sgminer.exe -k darkcoin -o stratum+tcp://stratum1.suchpool.pw:3339 -u x.1 -p x -I 11 -g 2 -w 256 --lookup-gap 2