on my personal boards, i kinda like having 'crazy' members like that -- makes everything a little more lively, and there's always something new.
but, on my corporate boards... it does get to be a hassle, and after awhile 'enough is enough' so to speak.
a quick fix is just really bumping up your flood control time. maybe even 3-5 mintues, if need be.
if thats too drastic, you might just try PMing the person -- find out whats up. maybe ask them to limit their posting barrage to ONE forum on your boards (possibly a 'misc' forum)