wired receiver, getting the red X with the number 13 underneath - need replacement?

Hi all,

Just last night, my set top box/DVR (Cisco IPN4320) decided to stop working normally; the channel guide was stuck on "getting information" for every channel and I wasn't getting any video or audio.  I've tried the following, but to no avail:

- Power cycle the DVR

- Power cycle the router/gateway (even though my internet works just fine)

- Reset the DVR by holding the power button for 10 seconds

- Hard reset/"disaster recovery" by unplugging the DVR, holding the OK and Down buttons simultaneously, and plugging it back in.

The link lights on my  DVR are always green, and during the first part of hard reset (with one gear on the screen), they blink, so it appears to be downloading something.  I also tried a known good network cable and different ports on my router, which didn't make any difference.

The hard reset gets me as far as the screen with 2 gears on it, where it doesn't appear to do anything for 5-10 minutes, then gives me the red X with the 13.  I've pretty much resigned myself to the fact that I need a new STB/DVR, but does anyone know what error 13 actually means?  The online troubleshooter is useless (it actually suggests I have a general internet problem, which I don't) and I can't find anything online detailing these error codes. Also, can I bring my DVR to an AT&T store and exchange it there on the spot, or do I have to ship it through the UPS store as detailed here?  Thanks.