Above.

I can usually play as far as the third level of the game before I turn it off, I try to save my progress, which usually works, but then when I load the game again and try and pick up where I left off, the save game isn't there! WTF?!

I have Windows 7 64 bit.

I think I read somewhere the username you type is case sensitive (but it's displayed in uppercase IIRC). So make sure you always type it in the same way.

There's also another thread (here) where a possible (but rather complicated) solution is posted if the above doesn't help.

Yep. The first time I tried to load a save it wasn't there. Typing the exact name I used brought it up though.