IIRC, the switch attached to those small wires simply grounds them to turn it on (similar to how ATX PC supplies work with the green wire). Since you floated the grounds on each supply, I'm surprised it even works at all.
What I would do is use a
double-pole single-throw (
DPST) switch and have the small wires on each supply hooked to each pole. That will allow you to turn both supplies on at the same time, yet only use one switch and still have them isolated. A DPST switch is basically two SPST switches in one package.
However, a DPST switch may be hard to find, so just use a DPDT switch and just don't use two of the contacts:
http://www.radioshack.com/product/in...ductId=2062499