Laguna wiper problem?

Hi,

I have a 2000 plate laguna mk1, and the front wipers have suddnely stopped working on intermittant, and wash wipe. (they still wash but no wipe) they still work normally on both constant wipe settings but nothing on intermittant, they will also stop wherever they are in the stroke when i move them to intermittant, I have checked the fuse and its fine. what could this be

Thanks