nuendo 5.5.1 crash

i am having a problem with nuendo 5.5.1.
every time i close the program it crashes, some times when i open the program it scans all my plugins again and that takes a long time.
i tried to uninstall and reinstall it and still it does it every time i close it.
i have to say that it does not happen in the nuendo 5.1

does anyone know how to solve that problem?

Ariel Berns