What type of prepreg are you using? - Also, what's your cure cycle? - Easy-Lease on glass should be very reliable at releasing epoxy-based prepreg following cures up to around 180'C so I'm very suprised to read that you're having this problem. If it's a conventional epoxy prepreg and you're not exceeding 180'C with your cure then the only explanations would be:

1) Contamination on the surface of the glass (sometimes you may have other release agents on there which have not been removed) 
2) Problems with the release agent itself (it could be old or have been left with the top off for a long time)
3) Major user error (it's been known for customers to accidentally use Mould Cleaner instead of release agent)
4) Application error (unlikely, as it sounds like you're using the recommended 6 applications)
5) Process incompatibility - for example curing at a very high temperature or using an unusual prepreg resin system which is causing an unexpected problem.

If you could fill in some of these blanks then hopefully we can identify the problem.

All the best, Matt