We recently lost RPC over HTTP connectivity. I have been troubleshooting this for the last few days following the MS Troubleshooting guide but was unable to find any problems.
I have just managed to restore connectivity by ticking 'Windows Integrated Authentication' in the Directory Security tab of the rpc site Properties. All other settings left as recommended (ie Basic Authentication also ticked, anonymous access disabled). Basic Authentication is also set on the client machines.
I presume this points to some kind of security problem, but can find no issues with our certificate (GoDaddy) or other security settings.
Hopefully the fact that enabling Windows Integrated Authentication fixes the issue might give someone who understands this better a clue?