Turns out to be the U-joint. What kind of money we looking at?
About $135 for the U-joint assuming you'll do the work yourself or have some local help:
http://www.partzilla.com/parts/search/Honda/Motorcycle/2001/GL1500CD+A/SWINGARM/parts.htmlDo yourself a favor and get a new boot too, #8 on the drawing. Re-installing the boot will be much easier if it's new. If you don't get a new one, spray it liberally with silicone lubricant and put in in a plastic bag to marinate for 1/2 hour or so.