Cubase Studio 5 won't start

Shut down my pc last night (Cubase working perfectly) and booted it again today.
Then tried to open Cubase Studio 5 (win 7, 64 bit) - but during the boot procedure, it died around “Initializing Midi Device Manager”.
I’ve reinstalled Cubase, did a Scandisk. And when I try to do a repair, it fails with the message “The file ‘VST3PR_Gate_242’ cannot be installed because the file cannot be found in cabinet file ‘InstallFiles.cab’.”
I haven’t changed my setup. There’s no hardware involved (I even disconnect the soundcard).
Does anyone have a suggestion what to try next?

Check this out: http://www.steinberg.net/forum/viewtopic.php?f=130&t=23576&p=151481#p151481