Plasma Screen Not Working - Audio but no picture.

I have a TEAC 106 cm Plasma T.V. ,Model: PLH4220SD, That I have just brought over from Australia. We unpacked it, no external damage, pluged it in and it worked. An hour later the screen went blank. Turned the power off then on and it worked again for about half an hour until the screen went blank again. Now we can't get anything from the screen, the Audio is OK. Now I realise this unit is from Oz but we are only using the AV inputs, not the tuner side as we are already aware that this will not be compatable in the UK. Has anyone any sugestions? The Plasma TV is about a year old. Cheers Archemedies