All VSTi's on Instrument tracks gone after importing audio

Pretty much all in the title.

I dragged and dropped an audio sample into a track and then Cubase was stuck for about a minute.
I managed to save and close, though I had an error message when reopening, something like “this project was created with Cubase 1.x, cannot open”…

When I reopened the previous backup project (5min earlier), all my VST instruments were gone, all I had left was the MIDI tracks with all the MIDI data…

I had to reopen a 30min previous .bak file, save all my settings as vstpresets and then reopen all the VSTi’s in my session and load these.
I never had this kind of bug before 7.5, that’s really weird. Maybe something to do with the new Instrument rack I bet.


Windows 7 Ultimate 64 - 12Gb RAM
Cubase 7.5 x64

Plugins involved : Massive, z3ta (bridged from x86 version), Sylenth1