You could also have an issue with a lot of light hitting the IR receiving window on one or more of the IR receivers. Question do you get the problems in the night time with all lights in the house off also. try that. If you still have problems take Steve's advice and Junk it for a hard wire system. I also reccommend that as well. Next put the RCA's in the MICROWAVE, set to high and cook for 6 min. Let cool, then eat.
IR to RF to IR is a poor, cheep way to go. Check out WWW.Xantech.Com, WWW.Russound.Com, WWW.Niles.Com, They all have cool hard wire systems that really work to.

Good Luck