Soundcard oscilloscope, one channel rolling

Hi
I've just built a sound card oscilloscope adapter, using this article.
The first channel on the oscilloscope works great, I tried it using a sine wave oscillator I made a while ago. The problem is the second channel. The waves are the same as on the first channel, but the waves are rolling sideways. I also tried a square wave oscillator with the same result, so I really think the problem is in the adapter.
Anyways, I don't really have a clue on how to troubleshoot this. Does anyone have any idea on what might be causing this?
Perhaps this is something you usually calibrate in the software?
I really don't know a lot on how to use oscilloscopes, which is kind of why I did this project.

Presumably you have to switch the sync from CH1 to CH2?, but as you have to pay to view the article you mentioned, I can't tell if it's done in hardware or software (or even if you only get sync on one channel).

Ok
The sync is defenately in the software. I'll look into that. Thanks for the help.
Edit:
I found it. Now everything works fine. Thanks