Since the first 64-bit versions of cubase & nuendo i hated the very “steinberg” solution to keep the two worlds in strictly seperate folders. This is - of course - very save, but also very annoying for the users.
During the last 6 month now i use a “hardlink” (thanks windows 7 and ntfs) from C:\Users(username)\AppData\Roaming\Steinberg\Nuendo 5 to …\Nuendo 5_64 and everything works fine!
I haven’t found any problems so far. Nuendo 32 + 64 both recognise the right plugin versions and every configuration changes (keys, prefs etc.) are valid in BOTH versions.
I don’t know why Steinberg makes no effort to clear this situation, because during this days of changeover from 32-bit to 64-bit world the “official” solution is very annoying.