Special Characters in Text Field

[Robtech]

i created a Username and password DB for my clients logging into my site. I used their email address as their username. On the web page I used a find command to access the area. If I use just the password it works fine, however when I use both or just the username it tells me it doesn't like that.

Is there a problem with the @ symbol when searching in a text field?

Thanx

Rob