SX3 to C5

I recently upgraded to C5, and the system automatically migrated all my saved work from SX3 (saved as cpr files) for use in C5. This seemed fine as it also moved some of my VST’s in to the program also. As my P.C is not the biggest or fastest in the world, I have a habit of using the freeze function on most songs/tracks to free up my CPU, the problem is that whilst I am clicking to unfreeze the files, it appears to do so, but does not actually unfreeze the tracks or intruments, allowing me to make any adjustments, I freeze the chanel as well as the instrument usually. What can I do to resolve this?

Unfreeze these tracks in SX3 before opening the project in C5.

Many thanks Jarno!