Are your .NET patches consistent across your environment? I just fixed a similar issue due to patches being inconsistent between various hosts.
Did you recently ran windows update on the servers related to the platform ? if you did you must make sure all servers running the same windows update "level".
In case you got only 1 server in your environment (polling +web on the same server), i would run the configuration wizard and select "website" in order to rebuild the website.
RD to the Orion server, Check and see if ATLAS is hung up.
I've had instances where a user was editing a map and had the process hang, making other maps unavailable.