Obvious is only that it crashes for you, and most probably only for you as noone else has reporeted this. And obvious is that you don't want to provide bug report. So why should we help you when you don't want to help us?
See about clean install.
Make copy of incomplete files and add them.
I haven't downgraded so I have NO EXPERIENCES in downgrading, you do it on your own risk, don't blame me for eventual problems please. Especially when new file system has been introduced with 2.5.0.0.
My advice how to solve your problem I have described in other post. And seems rest of supporters agrees with me. I reply you once again mainly because I remember you from previous forums, so I'd like to show respect to long time user. And straightly: I think that your thinking about this problem is just wrong and will lead you to more then less problems.
And perhaps you just need a clean install.