No Audio on 2 channels - S2 DT

Hi,

i had a S2 540xx box working fine. last week i went for the Big lot deal and got myself a S2 DT (649xx).

i installed it and it was working fine, may be i thought so. on friday night, i had crackling noise on few channels and video looked to go bad too.

now on saturday, i noticed that i dont get any audio on channels 4 & 5 using cbl.
i tried using the cable box and it had audio.

i tried cable to TV, cable to TV card and all had audio on the mentioned channels.
i have restarted the tivo 3/4 times and it has not helped.
Software version = 8.3-01-2-649

i have not checked with the customer support yet.
should i get a new box or open a case with tivo ?


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Edited to add details