Moving around some Domain Controllers in our Active Directory today caused a major issue with our Exchange 2010 Server. All of a sudden the Information Store was no longer available and a long list of errors occured. Alot of them complaining about the RPC connection not being made to the AD discovery tool.
Process STORE.EXE (PID=888). Topology discovery failed, error 0x8007077f.
After some frustrating debugging I finally found the problem in that one of our Subnets was no longer registered to a site, after this was added in Active Directory Sites and Services the Information Store booted as normal.