I am trying to install a .p7b cert on our ACS, I get 'Certificate file is in invalid or unsupported format.'
I know 2048bit certs were not supported in 3.3, is that still the case?
Yes it is still the case. Look at this doc and do a seach for Key Size-1024**
The doc states:
Note: The Windows 2003 Enterprise CA allows key sizes greater than 1024. But, the use of a key larger than 1024 does not work with PEAP. Authentication might appear to pass in ACS, but the client just hangs while it attempts authentication.