Vinyl distortion - What's the problem?

All the previous posts had good advice. The only thing I would add is to check the cable. Is it worn or in need of replacement? Is it attached securely?

Thanks for all the input. I adjusted the "bias" slider (is this the same thing as anti-skating?) as suggested by Newbee to be around .75-1 units instead of the 1.5 to match the tracking force as recommended by Rega. Seems to have helped a lot. Occasionally, there still seems to be a little distortion as the arm gets onto the inner part of the record, but I'll try to tweak my alignment to see if I can eliminate that.

sounds like you have good ears and are paying attention to what you're doing. you may now be hearing distortion in the record itself - i have a lot of records that distort near the end. i believe this occurs in the cutting process and there is nothing you can do to correct it. if its a set up problem you should hear this on most disc's (and i'll bet you don't). If possible i try to stay away from records which are over long on one side for just that reason.