one set of lights turns off the other

Ok this is my first time trying this website so dont let me down.

A friend of mine and i installed an underglow kit in my 1996 ford probe gt. when we went to connect the last wires we came across a problem, when we hook up both ground wires none of the lights work. when we disconected one of the grounds the side lights came on. we allso found that we can switch them. example: i can turn on the front and rear lights by them selves and they work fine. (they are wired together)  and i can turn on the two side tubes by them selves ( they too are wired together) but when both grounds are connected none of them will turn on. this is verry confussing to us so any help would be great.

ps we tried relocating the grounds to two different places one under the driver's seat and the other the passengers seat and it didnt work.

it is a pilot kit with the transformers seaperate from everything

please lett me know if you can help

What are you using for the power source?  Do you have a volt meter to do a little troubleshooting?

I ran a little wire form the battery and it's powering both transformers. i was talking to one of the techs at my dealership and he said that i might need to run a thicker wire to them and it might have nothing to do with the groung wire.