I have seen a fair amount of project corruption myself, and it’s usually due to one of three things for me.
Firstly I notice it when I’ve got a very complex and large project. This may say have many edits on many audio tracks, or rather a lot of automation, etc. Usually too many edits will tend to crash Cubase as well as corrupt my project. To avoid this, I always save numbered projects, keep everything that’s ever created in the project directory, and then periodically bounce the complex audio clips down to keep things a bit simpler.
The second thing I notice is that when I reach my memory limit (<2GB on XP, not tested in Win7) then the project will likely be corrupted next time I try to load it. I can see how much memory Cubase uses by using the Task Manager. It doesn’t corrupt while you’re using it, but when you save it and load again then it’s corrupt - a nuisance because you can be busy auto-saving corrupt projects for ages before you notice, all day sometimes! Also when the memory limit is reached I find that some instruments don’t load their presets correctly or at all. I avoid this by simplifying my projects and rendering things down to clips, samples or whatever I can so I keep away from the memory limit.
The third thing which causes corruption for me is rogue plugins, and specifically in my case AutoTune7. This is frustrating because it’s not like it’s ripped, it’s a full iLok’d version which I upgraded to last year (wish I’d bought Evo cause it would have cost me less!), but it just causes Cubase to do all sorts of weird things including project corruption, crashing on exit, pops/clicks, phasing issues, etc. So, now I disable AutoTune7 except until the last minute I can, then I correct things all in one go and disable it again, or use vari-audio.
So I guess, I’m saying, check for any of these issues and avoid them. Hope this helps.