Right, got a bit of a problem hopefully you camera experts can help!

My parents bought me a Panasonc fz28 as a belated birthday present, absolutely love the camera! BUT when i try to use the shutter priority mode if i select a shutter speed slower than 1/250 of a sec the brightness of the picture on the screen skyrockets until its completely white and images that are captured are the same...

Do you reckon this could be something wrong with the camera or am i being a bit of a div?????

Cheers