sounds like it might be the same problem as i had
is the wiper rubbing on the edge of the bonnet? and damaging the paint work?
the problem is maybe that the plastic linkage arm connection, connecting the driver side to passenger side wiper has broken/snapped!!
i believe there is two types of this assembly, the old one is all metal the newer one (from about 2001 onwards has a plastic link arm), youl need to find out which one you have.
mine was the newer one, if you have the older one this probably wont apply
if you pull the wiper away from the screen, it'l probably feel floppy and will rest against the bonnet
to fully check this out/replace you have to remove the wiper arm and then the black plastic cover's (they snap off okay once youve got one started but be carefull not to damage the windscreen!!) to gain access to the wiper linkage assembly underneath.
once youve got the driver side cover unattached youl be able to see underneath enough to see what the damage is!!
if the link arm is broken you will most likely need to replace the linkage assembly. this isn't too difficult just involves a coulple of holding screws and the motor electrical connection.
i couldnt manage to get hold of the assembly from a scrappy (approx £60-70) so had to buy from main dealer (ouch!!) which i think was about £120 and fitted myself
yeah very expensive for what it is considering if they would have made the link arm connection out of steel this probably wouldnt have happened!!
let us know how you get on!!