I'd have a go at letting someone fix your USB issue first, could be a very easy fix and
there are plenty of knowledgeable people on here.
As for Cubase, yes you can
transfer any project between OSX and Windows, just copy across your project folders, you
will need to have the same plugins etc installed on the mac to have the projects run
exactly as before. Also Cubase cannot open project files that have been created in later
I'd make a list of all your software and hardware then see if it is
possible to run it on OSX bearing in mind that the latest version is Lion and soon to be
mountain lion unless you decide to buy used (same rules apply).
But, first why
not tell us what your USB issue was?