I've searched the net wondering how I could trigger my Nikon flashes with my 580EXII in master mode using IR.
I've discovered that it is possible. I've set my xti to 1/200, f5.0, ISO 100. With my 580EXII (E-TTL mode) set to master with the flash head disabled fired my first shot. I turned 2 of my Nikons on aswell as my 580EXII (2nd unit off camera) in SLAVE mode. Both of my SB-80DX fired but my 580EXII did not?????? It appears there is some sort of interference to prevent my Canon flash to fire. I turned both Nikon flashes "OFF" and suddenly my Canon fired.
Here are two example shots #1 is a picture of all three flashes turned on. Please note the 580EXII did not flash. #2 is a picture of my Nikon SB-80DX turned "OFF" You will see my Canon now fires. All 3 flashes are set to 1/16 in Manual.