Hmmm That's strange - see Reply #1.
I don't mean to argue with success, but I question your definition of pins 2 & 3 - I think they should be reversed.
See page 7 of this - http://www.x10pro.com/pro/pdf/technote.pdf
Some of the confusion may have to do with the fact that most phone cables "flip" the wires on one connector. Hold the two ends together (as if you were going to plug them in) to see what I mean. One connector will be BRGY the other YGRB.) So if you use both RJ11 connectors on the cable, you have to account for this.
This fact also makes going by wire color misleading. If you just cut one of these cables, the color depends on what end you plug into the PSC05.
Using the diagram above, or in the link to the manual, you should
1. Zero crossing (BLK or YEL)
2. Gnd (RED or GRN)
3. Rcve X-10 (GRN or RED)
4. Xmit X-l0 (YEL or BLK)
Perhaps your setup is working because you don't use receive - I'm not sure. However pin 2 of the PSC05 should be ground (GRN in your case.)
What happens if you try pin 2 for ground now that you have it working?
I really doubt that they would make different models with different pinouts. That would be a real mess - even for X10.
I didn't intend to put so much time into this, but it may be useful for others.