Kala bass squeeky strings

Hi, I have been playing my Kala U bass for a while now and really like it. But the one problem that I keep getting is squeeky strings. I bought it at the beginning of last year and it has the original strings on it.
Its usually comes from my fretting hand but sometimes my picking fingures as well. If I am in the middle of a number I quickly lick my fingers which seems to solve the problem for a while.
Has anyone come across this? Can anyone suggest a way of getting rid of the squeek.
Hotfoot.