I have mainly seen this issue when running sage in a terminal services environment. It took me a little time to find out what the issue is and it is so simple!
A client was finding that when trying to run a report in sage he would get the error “the RPC server is unavailable”. I checked the rpc server service on both the terminal server and the SBS server where they store their data. All is functioning. As I was browsing through sage I tried to print and was not able to as there is no default printer. This is odd! Printers should be mapped automatically! So, simply logging off and back on to remap the printers resolved the issue!
If you find any other solutions please let me know in the comments section!