I read the link that Snowball posted, and the advice there is good. The first thing you should try, (and possibly already did), is to unplug the television, wait a few minutes, plug it back in, wait 30 seconds and turn the set on. Many of the larger screen televisions have additional circuitry for demag when the set is re-powered.
If you do need to degauss the set, and don't want to spend some pretty big bucks buying a degaussing ring, ask a local TV repair place to "rent" you their coil for a few hours. Follow directions posted in the link above, and remember, nice and slow is the way to go. Also do not shut the coil off until it is 5 to 6 feet away from the set.