Failed to Enable Constraints (SQL/VB.NET issue)

[NFSRacer]

Okay, but I tried without the NULL check box in the table design checked and got that same result. However querying the entire table means I'd have to do a ToArray to be able to use the data, right? I mean, how can I access the password and username independantly?

UPDATE:
I do remember doing another debugging session a while back to see what the issue was, and found the string being returned in each of the queries was the column name, rather than anything else! I mean, as far as I understand it in the query, it's returning a table, but the ToString is supposed to turn the only value on that table into a string to be compared, the GetUserName searching for and returning that username in the database, and the GetPassword returning the password associated with that username. The column that keeps getting returned I named 'login', and each time I tried, it came back with that string, instead. Could that be it?