canon mv800 trouble

Hi i bought my canon mv800 early last year and it has done me well in everything i have shot but yesterday i took it outside to shoot some scenes and after one shot i pressed the button to stop recording and the viewfinder came up with a message all in red saying "remove cassette now" I only own two cassettes and now my camera wont accept either of them.

Anyone know whats wrong with it? im stumped.