I had a recent job that the customer (really old guy) had his system hidden in a closet. A xantech system was in place, 291 eye, 789 connecting, etc. To see the system better, he put a neon light in the closet. I went there yesterday cause he was having problems. I get there use the remote...it works flawless...mind you, its a Sony RMVL900; a remote I highly recommend for $100 programmed we sell..does macros, etc. Anyway, we go to the closet, he turns on the light, I'm making sure everything is doing what it's supposed to..boom remote works 20% of the time. I physically take the remote to the closet, works great! The DVD player was at the bottom of the pile, and it's working like a champ. So at this point I know the Xantech is working....scratched hy head for a while, then it hits me. I turn off the neon light...everything works like a champ.

Here's what I would try:
(1) if it were me, and it was a pronto or nice remote, I'd somehow get tht neon light to turn off when the system is going to be used. You could use X10, lutron would be easier...but any "turn on" macro would turn off the light (first). When the "system off" macro was emitted, it would turn on the light (last).

Option 2.
Xantech makes sunlight versions of their eyes. SUN filters I think is what they call them. Problem though, the strength of IR reception is reduced and the angle of reception is reduced.