I am using Sitecore Glass Mapper for a new project I\'m setting up. We are using Sitecore 7.2, latest version of Team Development for Sitecore (TDS) code generation and the
Did you check your Sites.config and the default language for this website? There could be a difference between the language which is defined in your Sitecore languages folder and your configuration.
I had a similar problem with one of my projects where I changed the Sitecore.Context.Language to "nl" instead of "nl-NL". The glass mapper will return null, but Sitecore.Context.Database.GetItem will return an object in this case.