Just a quick thought re white flashes. Do the flashes occur constantly dring cue playback - or just at the start of the cue?. (the latter can be solved by putting a 01.s delat time on the insensity channel on whatever control desk you're using)

Does it happen at the same q point - or randomly during cue playback?
re smart-e's - are they powered from both ends?
what is the cable route?
is it screened or un-screened cat 5 cable?
what version of catalyst are you running and what MAC OS is installed?
Who were the servers hired from?