Is it on the G string that you have a problem? Has it been left near a Stingray for any length of time? If so, it's caught something called Stingrayitis. E, A, D strings take your head off, but the G just lacks something. I've noticed it on many rays I've played.
Joking aside, if it is the G string, try angling the pups up to the G a bit more, it helps.
If it's high up the dusty end on all the strings that you have a problem, I don't know.