Error while executing on update script in bulk editing

Error while executing on update script in bulk editing

I'm working on a database with aprox 10.000 records.
When I try to make a bulk editing I always get this error message:
Failed to Update Data.
Error occurred on executing deluge script
View error details
Error details for airports Form
Error occured while executing on update script.
Error Occured in process





I can't understand what this mean exactly, but I haven't any on update script scheduled.
If I try to edit records one by one everything goes well.
I allowed edit acces to support. The application name is "Airports".
I will appreciate if you can have a look.
What I was exactly trying to do was: in view mode, search for "congo" in "country_name" field, then select all the results and try to rename the "country_name" field with "Democratic Republic of Congo" (this is a simple single line field with any particular Validation requested".
Hope you can help.
Giovanni