What TV are you using? Did you update the software? If not, it could be that the chip that houses the STB got damaged. Just to make sure, are you looking at the Source and it says unknown STB in there, or did you really go into change mode on the PUC ..... maybe you can take and attach a picture.
Cheers
JK
BS9000, BS2300, BC2, BL2500, BL3, Bl2, BS1, BV8, BC4, A8