Please Help a Technically Inept Moron!!

..... the moron being myself

I recently purchased my dream bass, a '62 Vintage Precision (Reissue). Despite playing for 15 years i've never fully understood all the technical stuff regards my instruments and generally feel pretty stupid when in amongst knowledgeble people such as yourselves

Anyway, the problem centres around the occassional "dead" note on the A-string, I could be playing away on it and from out of nowhere a note will just cut dead with no sustain. It doesn't happen often but enough to cause me concern. Things that might help in any diagnosis..... I changed the action and pick up heights recently, I really didn't like the way it was set up when I got it, is there a chance the problem could be caused by something I did wrong? Secondly, I changed the strings from regular slinky's to extra slinky's..... would that contribute???

Sorry for the long winded yacking, any help or suggestions wiil be greatly appreciated as the problem is ruining what otherwise is a lovely bass.

 

That's the thing, i changed the strings, action and pick-ups at pretty much the same point in time so it's hard to identify what the problem is...... would it be worth a try to revert back to my regular slinky's to stop the "bottom out".... (sounds perverse)??

Cheers for the input!!!