I'm using Cubase SE at school for one of my GCSE compositions. I speant ages making this piece using about 10 different instruments, but every now and then, when I loaded up my song, all the instruments had turned into 'gun shot' or 'piano' and when I looked at the instrument panel, there was only standard instruments in there, and sometimes there was a list of all the instruments but there was no sounds in the folders . They used to come back if I restarted the computer, but now, they just won't come back at all.. When I open up the sound bank, it says they are all there.. but they arn't :S My school has about 20 computers with Cubase SE on them, and ALL of them are doing this. Any suggestions?

Please help, thanx