My Samsung 400CXN Magicinfo display started showing an error in a box which slowly moved around the display. The error indicated a fan problem. The monitor is 9 years old and the last time that this happened, it was still under warranty and so we sent it for repair. This time I opened the back panel, which is extremely easy to do. All of the fans were heavily clogged with dust. I vacuumed it thoroughly and re-assembled. It worked perfectly. Obviously work like this should only be attempted by someone who knows what they are doing - make sure that the monitor is switched off and be aware of residual charge etc. Thought that this tip might save someone a lot of money.
Nolly