James, it does sound like a corruption, but you may be able to import an old
one like this:

1. Create a new (blank) database.

2. Uncheck the boxes under:
   Tools | Options | General | Name AutoCorrect
Explanation of why:
   http://allenbrowne.com/bug-03.html

3. Import all the stuff *except* the bad form from your existing database:
   File | Get External

4. Import the bad form from a backup database.

If step 4 still fails, try opening the old database and saving the bad form
like this:
Open the Immediate window (Ctrl+G), and enter:
   SaveAsText acForm, "Form1", "C:\Form1.txt"
replacing Form1 with the name of your form.
If that works, open the newly created database, open the Immediate window,
and enter:
   LoadFromText acForm, "Form1", "C:\Form1.txt"

More general info on recovering from corruption:
   http://allenbrowne.com/ser-47.html