String or binary data would be truncated -- Question

I know the general reason this happens. But it makes no sense why it is happening to me. I have a .net app I developed on a windows xp machine. I created a package, and deployed it to win2k/win2k3 -- and for some reason when I run it on that box, which manipulates the same database, and does the same insert/update it fails. Could it be a dll issue ?

I know for a fact the string is well formed and the database contains the correct columns, because it works on my xp box. Any suggestions ?

this is what I get :

[SqlException (0x80131904): String or binary data would be truncated.
The statement has been terminated.]
   System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +857242
   System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +734854
   System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +188
   System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +1838
   System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async) +192
   System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) +380
   System.Data.SqlClient.SqlCommand.ExecuteNonQuery() +135
   vt_enhancements.WebForm1.btnUpdate_Click(Object sender, EventArgs e) +1900
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +107
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5102