Generally as you know the TV demagnetise's only from cold at switch on, but in extreme circumstances like speakers being to near or vacuum cleaners switched off near the appliance.
The TV's own deguassing circuit is not man enough for the job, it will over a time deguass and the picture purity will return back to normal, although this may take many months!
The best thing to do as it is new(and as such under warranty), is take the set back to the supplying shop, tell them the truth & if they value your custom, Ask them if they can manuelly deguass it for you (hopefully the shop has a repair engineer present) if they haven't, any repair outlet will do it for you and as you know it takes about 30 seconds to do the job, if they want to charge you it should be at a very low fee.
As no parts are required. hope this helps
Darren, February 2005