Very dense reading napster I guess from what you say that the 2 that work are originals on the mother board at back and the other 3 are 'addons'
Is that right.
Essentially what it all boils down to - there are too many USB devices plugged in for the power supply to cope with.
So the answer to the conubdrum is one of two things
1. Unplug any device that is not in use that session.
2. Get your self a self powered external hub
That is a USB hub with a mains power brick to make it power independant of the computer.