MS SQL Error

We are using ERP by name SCALA Version 5.0 realease 13a which runs on MS SQL Server 7.0 with Service Pack 4.0. This is installed on a Windows NT 4.0 with service pack 6a.

Problem:

Today while we were Posting in GL we sudden got the following Error.

error Type: MS-SQL server
Error Code 1: -10
Error Code 2: 2627
data File : DAT GL Gl06B103

Likely Cause: violation of %s constraint ‘%.*s’. Attempt to insert duplicate key in object’

Can you please tell us why this error appears and can we fix this error.