When I read your recommandation for refreshing the metadata of the data source, I get the feeling that in the case of an OLE DB Source, you select the table from the dropdown box. This is a big no-no. (see here. Point 4 to be precise). Actually, selecting a table from the dropdown is even worse than select *.

Always use a SQL statement to select the data from your source. However, this will not prevent SSIS to screw up the metadata. To refresh the source in this case, replace the select statement with select a = 1. Then, after the metadata is refreshed, paste back your original statement.