I have been having this problem too often.
My only fix is to shut down arcmap and restart.
I can't find why it is happening.
Anyone else see this?
export to pdf watch it go all the way through and when it should show the file progress (processsing) bar it just goes away and says export complete, but the file is 0kb.
arcmap 10.0 sp 2
Not only have I tried refresh, restart, shutdown. I have tried to open the file. the message is...

It seems there is something to do with either the original file or arcmap.
I tried to create a jpg "export" from arcmap and get the "can't map metafile to memory" error.
But another document will export both pdf and jpg.
Then a coworker opened it and exported immediately.
It also occurs on other machines though.
I cnan't nail down any consistent behavior except that it always doesn't show the file status bar after processing the data and successfully writes a file (0kb).