Some early M600/750's were fitted with Marzzocchi forks and had loads of probs with fork seals.Look for a 'M' stamped on the bottom of the fork leg,near the spindle.They usualy leak on one side if they have spent a lot of time sitting on the sidestand.
The seals have been updated as some where the wrong diameter,but they still leak.
There was a thread (on the SS board?) about leak proof seals,maybe the way to go.