VS 2008 Unbinding A DataGridView - Allow A User To Check / Uncheck A Row For Further Processing

I use a SqlDataAdapter to fill a DataTable and then set that DataTable as the DataSource for a DataGridView. All works well. Then I add a column at the beginning of the DataGridView that will allow a user to check/uncheck a row for further processing. All works well. Then I display this to the user. All works well.

Since there are many times when the DataGridView could be displaying hundreds or maybe thousands of records, I have a button that will "Check All" records and another that will "Clear All" records. These work fine, but I've noticed a serious performance lag. Other test code that I've got shows that in an unbound DataGridView, even a large one with 50+ columns and 5000 rows, checking or unchecking all of these fields takes mere fractions of a second. (One test with 50 columns and 50,000 rows still only takes 0.334 seconds to check all of the rows.)

In my testing (with my current code), checking/unchecking 500 rows takes 15 seconds. Is this because the DataGridView is databound? If so, is there a way to UNbind it (making it simply a stand-alone set of data)? I don't need to push updates back to the server, so there's no danger in removing any databinding. I've even toyed around with this (to make the DGV unbound):

[Code]....