It looks like we figured it out, from a working machine, copy: C:\Program Files (x86)\FileMaker\FileMaker Pro 11\server.pem
If Filemaker Pro 11 is open, close it, then try to open a remote database using Filemaker Pro 11.
Hey FileMaker Mod, how come the server.pem file doesn't always get created during an install?
Your solution worked perfectly for a problem that had been driving me crazy in our office. We are still on FM 10, but were having the same issues of certain users not able to connect to remote hosts for no apparent reason with the "either the host is not available..." error.