I've had the problem with mine but it was because someone had pulled it apart and did a crap job of sealing it back.. To get the origional seal apart I know there are abunch of fourums on how to do it but it consists of putting them in a oven and pulling them apart.. I only had to cut some caulking from mine but that's how you take them apart and then use some clear sealant to seal them back.. N while you got them apart clean out the inside of the lense it makes a big difference hope this helped.. I'll try n find a link
to a diy headlight forurm