Cannot insert duplicate key row in object ERROR

Dear ALL,

I have a simple data flow task in my package. What i'm doing is merging data from two different sources. The destination table has a field 'AgeOfActiveDetailID' which is the primary key and it is not from the source (i have no idea how its getting populated). What my package is supposed to do is add the data from the second source to this DESTINATION TABLE. When i execute the job i get the following error:

An OLE DB record is available.  Source: "Microsoft SQL Server Native Client 10.0" Hresult: 0x80004005  Description: "Cannot insert duplicate key row in object 'dbo.AgeOfActiveDetail' with unique index 'idx_AgeOfActiveDetail'. The duplicate key value is (Jan 24 1901 12:00AM, 49, 1, 13417500, <NULL>).".

Please need help

SV