either a gpu problem or a monitor problem
one side of the cable isnt connecting properly meaning that all colours, are getting through less than red, make sure the cables are inserted correctly and there isnt a little bit hanging out- if you need a new monitor i suggest,
http://www.alternate.co.uk/ASUS/ASUS+VH228D/html/product/871060/?
simply for its cheap price and excellent quality (i am running 6 of these in eyefinity)