Kenmore Direct Drive Washer Started Making a noise during Spin?

Our Kenmore clothes washer (Series 90 model# 110.28922791) just started making a noise while spinning. It still washes clothes fine - the only problem is the noise.
The noise is a rhythmic "thump - thump -thump", about 2 beats a second, that starts as soon as the washer tries to spin up a load. It's louder when it first starts spinning (when the basket is spinning slowly), then gets softer (same rhythm though) as the basket spins faster and faster. Noise continues throughout the spin cycle.

I took the cabinet off, but there's nothing obivous to my (untrained) eye.

So, is there anything I can check into to diagnose this?

Thanks in advance

guy
February 2007