...only to find that some coworkers had been messing with it! They knew I was having trouble with this bug and running out of time and so they upgraded my machine for me. Except it wasn't even on, they hadn't finished connecting all the parts. I couldn't believe they would be so dumb - I was just in the middle of debugging the problem and now I'd have to fix up this computer and get it back in that state and waste a bunch of time. I think I yelled a lot.
I woke up from this dream very very angry...it took me a few minutes to calm down. So I guess the lesson is: don't do that!