Unable to connect to Windows Server SBS 2011

I connect to a Windows network. We recently upgraded to a Windows Small Business Server 2011 server from a Windows SBS 2003. Previously I had been able to connect and view all files. I am no longer able to. I can see the server, but whenever I try to log in, it says that I have the wrong name or password. I have tried many different combinations of the domain as per my network admin. How can I connect? Is there something different I have to do. Please help me as my boss will force me to use a pc if I cant connect.

Thanks