damp around new window

[richardhoult]

during the summer we had a new upvc window fitted in our bedroom. during the recent heavy rain we have noticed a 2 inch damp strip inside the window that runs along the top of the window and down both sides to the cill. the surveyor from the window firm came to have a look and said that there is no problem with the window and advised us that water is likely to be getting in at roof level behind the gutter. however, my brother-in-law, who is in the building trade, questioned why it has only happened since the new window has gone in and said it is more likely to do with the window frame seals or drainage. we have been living here for 7 years and never had this problem with the old window. also, there is no evidence of damp around the downstairs window. what is the most likely cause pleas - window or roof?

[welsh brickie]

sounds like the havent sealed the window properly,Or they caused a crack when removing the old window and havent sealed it