CDT Speaker Problems (Static and cutting out)

Hi all
I just recently purchased a used infiniti g35 with CDT speakers, tweeters, and preamps. (http://goo.gl/pUec5) They are powered by, i believe, a 600watt kenwood amp and connected to a Kenwood headunit.

PROBLEM:
Randomly, the left and or right side speakers/tweeters will cut out, and once the volume is raised the about 25/40 (decently loud) the speakers will make a static-e sound and kick back in. The volume can be lowered for about 2 minutes but then the speakers will cut out again. Recently, it has only been the left speaker cutting out but there have been instances where just the left and both have cut out.

Do i need a new amp or new preamps or new speakers in general, or do i just have some bad hookups somehwere?

My Car: