When you say you restarted the 'BOX', was the database shutdown clean? Sometimes back, I tested trying to do copy the DBF files while the database was open, and tried doing a normal shutdown. It was taking a long time so I did shutdown abort. And when I tried to startup, I got the errors you pointed out.

So my guess is, When you restarted your 'BOX', some of your scripts might have been copying your DBF files and the database was still open. The shutdown may not be proper. Did you check your alert log file? Does it say more?