You must have bugged up the gpu setting on catalyst. Fo into your rig and pull out the pcie power cables from your 290 this will disable the card and re enable your mobo video output. now connect your monitor to your mobo. Uninstall catylyst. I mean everything. Now reinstall catalyst so you have fresh settings. Plug your power back into you gpu and plug monitor into gpu and you should be good to go.
Hope this helped
Or you might have fried it D: poor 290 D: poor wallet D: