I watched the console after realizing that it gets the first cable channel and then refuses to scan further.
Here's the relevent messages. I think the problem lies in the NSInvalidArgumentException line.
12/20/07 8:13:18 AM renfield-macbook recsched_bkgd[5018] recsched_bkgd 5018 com.apple.console Warning PROGRAM 1: 22.1 WLFL-DT
12/20/07 8:13:18 AM renfield-macbook recsched_bkgd[5018] recsched_bkgd 5018 com.apple.console Warning Exception during scan = NSInvalidArgumentException, reason: nil is not a valid object ID
12/20/07 8:13:18 AM renfield-macbook iOnTV[5035] iOnTV 5035 com.apple.console Warning Tuner changed - 1 stations on new tuner
12/20/07 8:13:18 AM renfield-macbook iOnTV[5035] iOnTV 5035 com.apple.console Warning Channel Scan Complete