Import supplier error

I have tried to import a list of suppliers (from the ADMIN>DATA EXPORT/IMPORT>EXCEL SPREADSHEETS option) but I keep getting import errors whereby the first supplier record imports but the remainder fail because it states the record exists.

The preview within the definition group shows all is well, and I have added the additional code to the import script that is required. I have also checked the Global Address Book and all seems ok there and I can manually add a second record.

Any ideas?