M_Boats: Main Haylard jumping the sheave?

Any of you folks ever had an issue with the wire cable on your main haylard jumping the sheave and then getting lodged and stuck? I've had this happen twice, requiring me to have to take the mast down and pull it back in the proper position. I keep my boat in the water, so it's harder to handle with a boat that is rocking back and forth. Any tricks you can suggest? Is there a fix? I may have skimped a little on getting haylard lines that are two small and therefore not "weighty enough" to give some counterweight to the opposite side of the mast, if that makes sense. Could that be a problem?