Perform - someone removed a row in your list

I believe the following error occurred either after deleting a column in a table that is in my perform screen or changing the verify join lookup field, but I am not sure: "Someone else has deleted a row which is in your list" I am running SE 7.24UC5 and SQL 7.20.UD1 on a Sun Ultra 10S with Solaris 2.6 OS. I assumed that the index was corrupted, but the data was ok, so I started fixing the problem by 1) unloading the table 2) running dbschema to an "tablename.sql" file and edited the file so it would later recreate the table. 3) dropping the table 4) recreating the table using the "tablename.sql" schema But, I still got the error when I used the same Perform screen. The only way I stopped the error from occurring is by generating a new screen for that table and manually editing the screen to match the original screen's lookups, instructions, and other modifications. Also, I examined the data in my unload file and it looked fine - there are only a few hundred rows. Even using vi from the OS, I was unable to read in or copy the old "tablename.per" file and compile it without getting an error. How does Informix "know" that it is the same "tablename.per"? Why does that error occurr?