Cubase SX3 invalid file help

Yesterday after a crash, i restarted my PC and Cubase ( SX3 ) but i was unable to open again the .cpr i was working at due to an “Invalid File” message Cubase was displaying.

The project is mainly based on audio parts, with just 4 vst plug-ins opened.

I tried to remove those plug ins from the vst folder and restart Cubase, still without results.

What shall I do in order to be able to open this .cpr again?

Thanks in advance for your ( highly appreciated) help.