I had a very similar issue with mine last year, 2002 Curvy S. It turned out, after I had my tame sparks take a look at it the starter relay fuse had melted away the housing and caused some wiring damage. Apparently this affected the electronic gubbins sufficiently to prevent the reg rec doing its job . (Sorry for the lame explanation but I'm no auto electrician). Any way I bought a new reg rec whether it needed it or not and my mate rewired the starter circuitry and put in a new fuse holder and Lo all has been well ever since and I haven't had any further issues.

Before the job was done the bike would run out of electricity before it ran out of petrol . It just wouldn't charge at all during normal running, my mate told me the motor was essentially just being kept alive by the battery. If I stopped and attempted to re start the engine just wouldn't turn over, all I got was a clunk and that was it, no lights, nothing.

I hope this helps a little bit and points you in the right direction.

ATB

Paul