Guitar/bass grounding issue?

[ckyratm]

You know the humming/buzzing noise that some guitars or basses make when plugged in that usually goes away when you're touching the strings or other metal part on the instrument?
Well what is it when your guitar/bass does the opposite of this? My friends bass is having this problem and we were wondering if this was an easy fix.
Any ideas?

[Ohara]

Sounds like you have a grounding issue of sorts.

Check the amp first by testing with a second bass to ensure it is not starting inside the amp.
Check with a second amp as well, just to eliminate
If it is within the bass itself, first start by changing the patch cord
still there, you will more than like have to check within the bass itself, to ensure all wires and connections are in top shape. You could also shield the cavities while inside as you will have it apart anyways
From here if it still continues you may want to seek more professional help than I have to offer, this is just the steps I would take to rule out the humming.

[TheOrangeJuicer]

The bridge is likely not grounded.