just thought I'd share this with you as I only found this out recently. When XSI crashes, you'll see the dialogue box that says "Failed to save sequence before system failure"
Most people just click on the okay button which will tell xsi to quit, however if you don't press the button you can still go to the file menu and save your scene ! I always assumed when this box came up you'd lost all your work :surprised
A lot of you probably already knew this already but I thought it'd be worth sharing for those of us new to XSI,