I almost forgot, from time to time it seems its going to download the requested file, but when I open the file it only contains the following error:
The following error occurred:
[code=CANT_CONNECT_LOOPBACK] Cannot connect due to potential loopback problems
Please contact the administrator.
I just had this exact same issue.
The DBA determined that it was caused by the order in which the report services were started. I didn't catch the exact details from him when he told me he had fixed it but the gist of it was the BIEE service has to be started after the admin service. Or vice verce
Hope this points you in the right direction at least!