A few other suggestions: Try copying the most recent Money file to your internal hard disk and opening from there (try the same thing with the most recent back-up file, opening through Money's Restore Back-up function). It sounds like your external hard disk is going/has gone bad. Check it with Norton Disk Doctor or something similar. It is also possible that the problem is the cable between external HDD and the computer; check it as well. Try changing to a different port, if your computer has more than one port. (I don't think you would get the same messages if the disk were full, but I am not certain.)
If the external HDD is going bad, you probably have more than these few files that are a concern. You may need to take it to computer shop to have as much as possible recovered. In the meantime, back-up as much as you can.
Post back and let us know how things go.