Users script changing password problem

hi ive been using asplogin script, and theres a problem with the user or admin changing their password, the problem is with this line of code can anyone tell me what the problem is?

trPassword = md5(Replace(Request.Form("txtPassword"), "'", "''"))

thanks

may help if you have the whole of the code

If Request.querystring("mode") = "changepassword" then
userID = Clng(Session("userID"))
If Request.Form("txtPassword") <> "" Then
strPassword = md5(Replace(Request.Form("txtPassword"), "'", "''"))
strSQL = "UPDATE tblUsers SET tblUsers.password='" & strPassword & "' WHERE ID =" & userID
adoCon.Execute(strSQL)
Set adoCon = Nothing
Response.Write ("Your password has been changed.")
Else
Response.Write ("<form name='Profile' method='post' action='users.asp?mode=changepassword' onSubmit='return TheFormCheck()'>")
Response.Write ("<br><b>Change Password</b><br><br>")
Response.Write ("<table width='400'><tr><td>New Pasword:</b></td><td><input type='Password' name='txtPassword'></td></tr>")
Response.Write ("<tr><td>Repeat New Password:</b></td><td><input type='Password' name='txtPassword2'></td></table>")
Response.Write ("<br><br><br>")
Response.Write ("<input type='image' src='images/submit3.jpg' name='Submit' value='Enter' alt='Enter'>")
Response.Write ("</form>")
Response.Write ("<br><br><a href=main.asp><img src='images/back_16.gif' border='0' alt='Go Back'></a>")
End If
End If