Philips 28dw6557 problem

I recently bought a Philips 28dw6557 digital TV.
However a problem soon became apparent.
Sometimes the TV would get stuck on the digital station you were watching and you could not change to another digital station, also the digital teletext would stop working.
The picture did not freeze up, the TV just refused to change channels, even the channel change button on the top of the TV would not work.
You could switch to analog with the A/D button and everything worked fine, channels changed, teletext worked ok.
But go back to digital and you were stuck on one channel with no way to change, even the OK button would not bring up a channel menu.
The only way to fix this was to switch the set off and on again.
So the TV was replaced, but it soon became apparent that the new one had the same problem.
Also the picture was worse on the new TV, noticable distortion in all four corners, seen worst on digital teletext, and the bottom right corner slightly out of focus.
So the second TV went back and a refund was obtained.
What was going on, and why was the problem the same on 2 TV's?

Hi I have this philips TV

and the problem you mentioned only happened twice in 3+ months of use...

and this happened when I was trying to change digital channels too quickly and pressing too many buttons too quickly...

I think it was probably a crash of the Operating system for the digital tuner, which resolves when you put the TV off and on again (not stand by)

I have no picture problems at all...

regards

Thanks for reply.
However I noticed that the problem occured after I'd been watching TV for a bit without pushing any buttons, eg/ watching BBC2 for 45 minutes and then trying to change channels, the digital channels refused to change, almost as if the TV computer had gone to sleep.
It was an intermittent fault, but not due to pressing buttons too quickly in succession.
I noticed that the last time this happened I pressed a button and there was a "click" on the sound and the channels would not change.