Access overwriting records

Hi

My company has an Access database in which contact addresses are stored. The database has exceeded 5000 records and when new addresses are added, they overwrite older (different) ones. The database was set-up by a previous employee, and I cannot find a solution to this.

Is it possible to set a limit on the number of records that Access can create in a database? Is there an internal error that can create this problem?

Please help.

Thanks