TV not reponding to remote

Question

I have a Philips 27T500 C101 TV that was working well, but one day when adjusting the PIP the TV stopped responding to the remote. Batteries in the remote check out OK at 1.43 volts each. Power button works on the TV as do the Channel and Volume buttons. But I miss the mute feature of the remote when those commercials come on !!

I bought a Philpis Universal remote but none of the program codes would make the TV respond. I was able to program other codes for the remote to control the Sharp VCR and the KOSS DVD, so I beleive the remote is OK.

Any suggestions ?

Thanks