I was thinking that when you tried the MOV across the transformer primary(120 volt side) you might have accidentally switch the mode to a different pattern, other wise like Gar says the MOV would not have any effect on the load? some of these mode switches are electronic, and switching on and off the power could cause the mode to change. do you have a web site for the lights?
seems strange these lights don't come with there own power supply? But then again I find it strange the the NEC doesn't require them to be listed as an assembly like it does for other low voltage lights:roll:
The 12v LED lights in the pool are the kind that you program by cutting the switch on and off in a specific pattern. That is what is creating the problem with the switch operations kicking out the GFCI breaker.
I talked to the manufactures support today and they said this is not a problem they are familiar with. So I believe I have a bad transformer or a bad light.
Here are links to the fixtures for those who are interested.
http://www.nexxuslighting.com/pool/support/pdf/InstallManuals/Melody_Blanco_Install.pdf
http://www.nexxuslighting.com/pool/support/pdf/UserGuides/UserGuide_SAVI_Pool_Spa_M4-SA.pdf