Roof Leak 2000 3.2 S Boxster
 

Hi folks, sadly, this morning, after parking on level ground; with light overnight rain, I discovered a couple of drops of water on the insure of my 2000, 3.2 Boxster S at the point where the roof meets the windscreen(windshield) passenger side.
This is the 1st time i've seen this. It looks like my roof could be tighter- it's closing fine and I cannot see anything untoward outside or inside.

Any suggestions on tightening the roof or fixing this prob?
Many thanks,
T