help needed!!

[Megahackerd]

hello
recently built a computer (its about 1 week old)
everything was fine apart from today
the screen resolution was at 640*480
before was at 1900*1080
a cant change the screen resolution because its grey
using hdmi
the vga cable seems to work but when in hdmi


specs:
amd 6300
m5a97 evo r2.0
msi 7850 2gb oc
patriot viper 8gb black mamba
seasonic s12II
monitor: benq gl2450hm

thanks in advance