Errors in IF Statement when using a copied date.

I have a column of dates that are a v-lookup. I copied that column to a new column using the paste special and values. I tried using that column (s) in an if statement but getting incorrect results.

I tried =IF(S8="","TTL",IF(S8<=$F$1,"NA","x")) where F1 is a date that I'm comparing to. I get x in my results even where the date in column S is less than F1.

I tried various options that I see on the forums including:
=IF(S8<"10/01/2011"+0,"NA","x")
and
=IF(S8<=DATE(2011,9,30),"NA","x")
each with the same result. However, If I manually type the date in column S it come out with the correct results.

There are too many rows to manually type this and we want to re-use the spreadsheet over and over.
Can someone help me with this?
Thanks!