Just FYI.. I have also tried with Antivirus disabled and Windows Firewall turned off. Nothing makes any difference.
here is the most likely cause and a solution: FMP installer does not install server.pem file
This is one of many acknowledged bugs that can be found in the Known Bug List here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: http://www.4shared.com/file/8orL8apk/FMP_Bugs.html
This solved my issue...
To rehash... Quite simply copy a file from a working machine to the effected one....
Specifically copy server.pem from the Filemaker installation folder in Program Files to the same location on the effected machine. After it's copied all is well.