Login Form Help!!! Run-time Error: '2471'

Hi Guys,

I am trying to set up a login form in my DB. I have followed the instructions from some of the previous posts on this site.

I have a table called tblUsers with 'UserId', 'UserName' and 'Password' as the fields. I also have two text boxes 'txtUserName', 'txtPassword' and a 'cmdLogin' command button on my form with the following code:

Private Sub cmdLogin_Click()

If IsNull(Me.txtUserName) Or Me.txtUserName = "" Then
MsgBox "You must enter a User Name.", vbOKOnly, "Required Data"
Me.txtUserName.SetFocus
Exit Sub
End If

'Check to see if data is entered into the password box
If IsNull(Me.txtPassword) Or Me.txtPassword = "" Then
MsgBox "You must enter a Password.", vbOKOnly, "Required Data"
Me.txtPassword.SetFocus
Exit Sub
End If

If Me.txtPassword.Value = DLookup("Password", "tblUsers", "[UserID]=" & Me.txtUserName.Value) Then

DoCmd.Close acForm, "frmLogIn", acSaveNo
DoCmd.OpenForm "frmWorked"

Else
MsgBox "Password Invalid. Please Try Again", vbOKOnly, "Invalid Entry!"
Me.txtPassword.SetFocus
End If
End Sub

Unfortunately, this code is not working in my database (MS Access 2000). I think the error occurs on the line on which it checks the password against the stored password (If Me.txtPassword.Value = DLookup("Password", "tblUsers", "[UserID]=" & Me.txtUserName.Value) Then).

I get a Run-Time error'2471' message saying "The expression you entered as a query parameter produced this error: 'The object doesn't contain the Automation object for 'smith."
NB 'Smith' is the user name entered into the login form 'txtUserName' box.

Any idea why this may occur? I would be very grateful if you could let me know please.

Thanks alot for your time. And keep up the good work guys! :)

Kind regards,

Zaf