Sign for underscore is missing in user name field of facebook app

[GoogleCodeExporter]

Hi, 
I have found a small miss with this app. The sign for "_" can't be accessed 
when typing a user name when logging in to the facebook app. The comma-button 
which contains this sign is then replaced to @. 

I would say that this is a big issue since you can have a user name with a "_" 
in it. 

regards, 
dave 

Original issue reported on code.google.com by [email protected] on 2 Jan 2012 at 9:32