In the first post, you said that you installed a master and a slave. I assumed you meant the pair of X-10 units that replace a pair of 3-way switches.

In the second post, you have a dimmer and a simple on-off switch, which do not describe X-10 devices. I'm really confused!

If you installed one X-10 unit in each box (opposite sides of the room), then it doesn't really matter which one is which to try my suggestion.

How about telling me what was in each box before you started, and what is in each box now. Also, did you note which wire was on the dark (common) terminal on each original 3-way?

Larry
www.fineelectricco.com