Check your network / ethernet cables. Swap them out for a new cable and see if the issue persists.
Make sure both devices IP Mode is set to the same function; ie...
Directly Connected = Static Self Assigned Mode
AVB Switch + Router = Dynamic Mode
You will need to access the RM via network or firewire connection to check network settings OR use the Press Button IP mode trick to force the RM into the desired network mode without software. See KB Article HERE for that process.
If you cannot figure it out, contact Tech Support via Support Ticket with this issue. They'll troubleshoot the issue with you.