i thought of something yesterday. Could that cap on the tone control have gone bad? check it out.

update plz user (com?)

Obvious, and sorta already covered...but have you checked the neck/body joint? If those bolts get stressed 'till they are loose, that will make your bass sound like shit. If you are as rough on instruments as I am...well, I'm speaking from experience here.

Do you keep it tuned to standard all the time? Is the neck warped? A common issue, I've found.

Have you cleaned the pots? Dirty pots can leak signal to a capacitor you aren't using.

Can you bypass the actives on the thing? A 5-minute soldering job...just run the pickups straight to the jack for a test. It will sound crazy different, but you will know where your problem is...