Hau Rock

I've had a set of promedia 2.1 speakers for about 2 years now, I got them as a gift and they have worked like a charm upuntil now, with only a few minor issues. Now, though, they have suddenly decided not to work as they should. For some reason, the preamp connection is incomplete. I can usually get the 2 speakers to play just fine, by jiggling the preamp cord a bit, or sometimes the subwoofer, but for some reason they will not play at the same time. I can't figure out why. has anyone seen this problem or have any idea how to fix at, or even how to figure out what's actually wrong?