The history so far:

1) Once upon a time there was the file "1234"

2) I did pack&go of him into "1234_rev0"

3) I modified file "1234"

4) I did pack&go of the newly modified file "1234" into "1234_rev1"

5) Both "1234_rev0" and "1234_rev1" prompt a blank error message when their drawings are opened

As title says, I get a blank error from 2 files and only them, I get no problem at all with the original file "1234".

The modification where quite straight: just edited a couple of dimensions, a view style and two notes.