formulas conversion between 6.52 and 7.0

["SR" <raftsp@xxxxxxxxx>]

Hello
I have been using version 6.52 for windows and now want to try v. 7.0
professional, but my formulas, systems and experts cannot be converted
correctly. During conversion I always get error messages and/or strange
symbols in the formula editor window. I also tried to import my formulas
after the installation of the new version, but the problem persists. Any
ideas ?
Thanks
Spyros