ok... let's figure this out.
how is your system set up?
where are the splitters?
is there one splitter and an a/b switch?
does the cable that bypasses the tivo box go straight into the tv?
i'm sure we can get to the bottom of the problem....

Splitter 1 goes into the modem and another splitter. Splitter 2 goes into the TIVO input and the VCR input. VCR output to TV input (coax cables). TVIO output to Video 1 input (via av/cables).

Can you determine who is generating the closed captioning? Is it Tivo, or the TV? is there another TV you can hook the Tivo up to when this closed captioning is occuring?

Tivo doesn't decode closed captioning, that's a TV function. Tivo just passes the signal on.

Have you tried hooking up the DVD player to the video1 input and seeing if the captioning is still on?

Ya, and it's not. This is so weird. The VCR is off too and there are no captioning settings on there.

Ok.. Now I'm really confused. Now the captioning is coming through on the regular TV. I don't get why, since it's set to off (I just checked).

What model/version of Advent tv? Maybe there's a known bug.

I don't have a clue. It's a few years old. I think it's just the TV.

Thanks for the help everyone!

Try enabling the CC on the tv, then disable it. See if that makes any difference

Ya, so I'm a giant dork. I was at my friends last night enjoying my margarita when it hit me.

When my TV is on mute the captioning is automatic. Since I run my audio through my sound system I mute the TV.

This message brought to you by your friends at Jose Cuervo.

Thank you everyone for all your help!

It's almost always the simplest, most obvious solution.
Glad you figured it out!