I have noticed this on Mac OSX 10.8.5 and cvmfs 2.1.15. When moving the laptop from work to home with the filesystem mounted, accessing new files in the mounted filesystem started getting Input/output errors. If I set the proxy with cvmfs_talk, it works only if I use an IP address. If I set the name server, the names start working. I don't know the details on Mac OSX, but I know that there's a way for the operating system to notify applications when the network IP address changes. On Redhat Linux see dhclient-script, which appears a bit different on EL5 & EL6.
One possible way to ";fix"; this would be to just document things that the person who configures cvmfs has to do.