I need help with this, cause it's driving me nuts!

My providers (Cox Cable, North San Diego County) recently remapped their QAM HD channels from their previous locations (8.1, 10.1, etc.) to new ones (708, 710 instead). From what I'm told, both of these channel number systems are now running in place concurrently.

This morning I re-scanned my Magnavox 42MF431D to make sure I had all the channels I was paying for. This model unfortunately does not allow me to input channels manually; it must autoscan to add channels. After the rescan, not only were my old QAM channels not detected (they were working before the rescan), but the new 700-series channels don't detect either, although I can tune these on the other two HDTV sets in the house.

I have repeated the rescan procedure several times, even going so far as to disconnect all the other TVs from the cable and turn off my Internet cable modem and router. I've direct-connected the TV to the main cable line. I've turned the gain on my Leviton signal distribution block up to +15 dB, hoping to boost the signal to the set to get it to detect these missing channels again. No luck.

I've chatted with a Philips support tech, who tells me that there are no software updates for this set (since 2006 :P ) - in fact, Philips have removed even the manual for this set from their support websites - big help they are.

I've scanned my printed manual looking for a way to reset the set to "out of the box" factory default, with no luck, thinking this might help. I'm at my wits end - I know the channels exist, and the other sets in my house can see them. Any suggestions? I'm ready to tear my hair out!