Freezer packed up?

The freezer temperature is showing as a flashing -- and has stopped working, the fridge is still showing as 4degrees and seems to be functioning. Weve taken the back off and vaccuumed it but still no joy. We've also tried turning it off and on several times. There is a warning exclamation mark as well in the middle bar but this might be because the filter needs replacing.
Any thoughts?

Titanic
February 2012