Thanks Kvaalen
I have fixed it, I am probably the only guy in the world who has had this problem
but if anyone else does what I did was ..
1. select top poly and hit 'copy'
2. deselect everything then hit 'delete'
3. hit paste
4. hit 'k' to kill the poly so your just left with the points
5. select the points in order in clockwise direction
6. press 'p' to make a poly
7. extrude
8. BEVELMANIA !
Scott