My '01 started doing this a few months ago. Not all the time and sometimes it'll blink fast for a few seconds then slow back down. I'm thinking the handlebar controls need to come apart, checked, and apply some dielectrical grease to everything.
Next time it does it you will find that one of the lights isn't working. This isn't in the switch but in the wires to the light that isn't working or the bulb itself. It used to happen to my Shadow but I never remembered to track it down when it was doing it.
Ok, moving further along, it is now a couple of months later & it happened like this The blinker problem returned & had gotten much worse (right blinker often just did not work, left blinker had to be held to the left before it would work) I called the local Honda dealer & ordered a replacement switch block Honda Part No 35020-MCW-D00 He charged me $120 Au, the list price is about $128 Au It now works perfectly every time Oh by the way this is the switch block with the passing switch on the front for those of you who have lame clueless lawmakers who have outlawed that function