Front wipers only work on high speed

Hi,

Just bought a used Octavia 1.6 GLXi Estate from '00, and am quite happy with it. I'd be even happier though, if I didn't have the following wiper issue.

It's raining today, and I went driving for a bit with no probs, parked the car for like half an hour, then drove off again only to find that the wipers had gone weird. They'll only work in the fast mode, setting them on normal speed, interval, or the "touch" mode does nothing.

Any ideas? I'm guessing it could have something to do with moisture as the problem appeared after having the car out in the rain for a bit. Relays?

Any help would be much appreciated.

Thanks!

Alex