Delete problem

I am trying to create a script that will show users online without using global.asa.  I almost have it working besides one thing.  I want my sql to delete entries in a table once an entry reaches a certain point.  So here is what I have.  My problem is it deletes everything in the table.
Suggesstions.

Here is the code:

strTimeout = 5
StrOnlineTimedout = dateadd("n",-strtimeout*60,onlinedate)

StrSql = "DELETE FROM active_users WHERE Last_Seen < '" & StrOnlineTimedout & "'"
adoCon.execute (StrSql)

I am using an access db and the column Last_Seen has a type "memo" and the form that the date entered into the column is 1/3/2004 2:40:17 PM using the now() function.

Thanks

I tried that when I do that I get this.

[Microsoft][ODBC Microsoft Access Driver] Data type mismatch in criteria expression.