Corruption after deleting a field

Upon upgrade to FMS8, it became apparant that our file is corrupt. FMS8 noted the corruption about 4 hours after regular use and shut the file down. I can recognize the corruption by the inability to import a particular text field (results) in one table (Results), only 10% of the records will come across to the clone of the corrupt file. All will come across if a new database is created and all will come across into a new text field created in the cloned file. As much as Filemaker tech support and I hope this is data corruption, it is more likely file structure corruption. They are currently examining the files.

I went to my archives and pulled out a clone of the development file used to make the live files and same problem importing the records. I then starting checking the files saved during development (I save a copy about every hour) and found a good file, and then a bad file saved 1 1/2 hours later. The good file clone can succesfully import the records from it's original file and the current live file that is corrupt. The bad file cannot do either.

The biggest change I can see between the DDR of the good and bad file is the deletion of a calculated field in the table causing problems. This calc field was a text field simply a set field of the text field that is corrupt. I originally had planned on showing the users this calc field instead of the text field to prevent the user from modifying the field but changed to a validation method and deleted the calculated field.

I have checked for illegal characters in the development files and found a few unusual characters such as the micro symbol but no line feeds... Both the good and bad file recover without any suggestion of problems.

Could this deletion have caused the corruption of my database? How could I have known about this corruption during my development phase of the project?

THANKS