Trees,trees+Invisible wall ?

[cid228]

Okey ..here it goes ..ive just made my island beutifully green with the extremely good lookin Oak-trees from OFPR.
(dont get me wrong ..im no tree huger if u think so)

Then when I play the game and comes running away from like 20 russkies, heading for the woods ..the bam ..oh ..theres a invisible wall around the woods !!!???

How do i get rid of the config that makes the square of woods hard as steel?
The Pine forrest works as normal ..just the oaktrees mess it up ...