According to a certain website which has touring plans on it, put out by the unofficial guide to Disney, low crowd weeks include 1/26/08 through 2/10/08.
Crowds will be bad 2/16/08 through 2/24/08 -- I would avoid that timing.
Then it looks like low crowds again until March 1st--when everything starts picking up.
Your best bet would be the last week of January. Good luck!