Fender Jazz Bass electrical problem?

I have a new Mexican Jazz Bass that I think might have an electrical problem. I've had it for less than two weeks and all of a sudden unless both pickup volume dials are at max, there's a loud hum. Same deal when either of the two is turned down even slightly. It wasn't doing this before today. Any ideas?

Thanks.

My mexi Jazz behaved a little better with a peace offering of better-quality cables.

You can improve it a little by earthing the magnets.

Does the noise sound a smooth hum, or a staticy (sp) hum? Does it increase/decrease when you take your hands off the strings?

If you run one of the two pickups louder than the other, you will get hum as they are out of phase. This can be corrected by any decent guitar tech with a little re-wiring. As far as hum when both pickups are set at the same output - this is definitely a problem and should be checked out.

That's a mexi jazz for you. They're notoriously hum-ridden. If both pickups are dialed all the way up, they act as a humbucking system.
The more you decrease the volume on either one, the more hum you'll get.

(All stock Jazzes are this way to an extent.)

This is 60 cycle hum, and is inherent in single coil pickups. Even upper end manufacturers who use the same style pickup have this humming when one pickup is "on" more than another, i.e., when a blend knob is turned off center, or in the case of two volumes, one is up more than the other.

Except the ones with the "noiseless" pickups which aren't single coil, but
"stacked" coil.

And Fender considers this acceptable?

But why, if they are all like this, did it all of a sudden happen?
I've played through loud amps before and never got that.