The first thing I would check is the levelwind worm gear, and the pawl that goes into it for wear, and make sure that it isn't gummed up.
Other than that, if the problem occurred under a fresh respooling, did you run the line through all of the guides on the rod? If you only use the first one or two, you could have the line at an angle that favors build up on one side of the spool.
To double check things, walk out all of the line and wind it back on, or drag it all out behind the boat and wind it back on.
Joe