Import data error while delete rows in the destination table

Both SQLServer2005, different server, import tableA from serverA to serverB.
When we import tableA for the first time, serverB will get the whole
structure and data of tableA. So far is fine. By the way, we need to change
the type of a column from varchar to nvarchar.
Second time, we want to save the original structure and delete the exist data.
So we choose the "delete rows in the destination table" property. But when
we execute this, there is an error below while validation.

/******************
Error: 0xC02020F4 at Data Flow Task: The column "dbname" cannot be processed
because more than one code page (936 and 1252) are specified for it.
******************/

All the columns in this table have the same errors.
I don't know why. Thank you.

If you made this operation in a SSIS package to work , you have to change the property AlwaysUseDefaultCodepage of a OLEDB Source in a Data Flow Task . The value have to be "false"