If your mast sheaves were originaly intended for wire with rope tail,
the sheave groove would have a normal radius groove with a shallow
smaller groove for the wire., now that your using all rope halyards, you
should change the sheaves to a standard radius.

When you 'sweat up' your halyard with the old combination, the wire will
seat in the shallow small groove, while hauling the sail up the rope
rides smoothly in the larger radius. Once you switch to rope, the
halyard load cause the line to deform into the old wire groove (not good
on the line).

I agree, you should drop the mast and see what you have..

Steve
s/v Good Intentions