I have luck sometimes with opening / closing the plugin (editor) until GUI shows up
but it make Cubase crash (is it cause or effect ?)
Very bad crash i usually i have warning like
“automatic save couldn’t be done because project is corrupted”
then
1/ i cannot save under another name / impossible to save (!!)
2/ last backup is corrupted
hopefully (!!) i have crash today which generates a crash report 
i’ll search where to find the file / how to send it @ steinberg.
NB : all my plugins are the same on the two comp and are running fine with C5 / Win 7
i’ve been using this config for the last two years everyday. only problems where when i was reaching memory limit