...from what i can gather you have exported from qxp 7 at home to 6.0, then burnt to disk perhaps, to then open at work in 6.5?
...when you export from 7 to 6 it gives message of 'file is already open' usually means you are trying to overwrite a file that is open in 7, which means you have to save to a different name or location...
...ensure you also export to single language rather than multiple language format...
...another thing to be careful of is burning to disc a quark file you have open, which is the same one you are trying to burn to disk, this can lead to corruption...
Andrew