Missing Freezefiles

I use the latest 6.5… Cubase version 64 bits on win 7 64
Cubase looses freeze files. “Missing Freezefiles”
Using jbridged Philharmonik vst instrument 32 bit
And fx on vocaltracks UAD 32 and Clariphonic and Autotune

Never had this before. The freezed tracks just don’t sound and when restarting Cubase can’t find them.
So I unfreezed and Freezed again. The same.

Anyone have a clue. Our engineer is getting nuts.