I have 2 WAN sites that lose their connection with each other daily. We have discoverd a strange way to temporarily "fix" the problem. When site 'A' tries to ping an IP address at site 'B' it times out, but when site 'B' pings an IP address at site 'A' it times out once and then connects without a problem. After 'B' pings 'A' everyone can connect to both sites and all is well for the next 24 hours.
Each site consists of one DC that also functions as a file server and 3 - 10 workstations. Both servers have a static route to the other, and so do the workstations.
The servers are all running Windows server 2008 r2.