Timthumb issue – URGENT

Hi All,

Spent ages moving a WP site from a linux/apache host to a windows/IIS host, its all working except one thing.
The site uses the centitia theme which has a couple of images on the front page controlled and resized by timthumb.php.
The problem is they dont display, i just get the normal x in a box.
The image paths in the back end are correct as i can open them in IE by putting the direct link in.
timthumb has required permissions on the cache folder which remains empty.
So i am a little stuck!
I have deduced that the issue does lie with timthumb but i cannot put my finger on what exactly.
Any ideas?