OK, this is a strange one. I have some users that cannot Ping one of our servers after about one minute.
I'll start a continuous ping, it will reply fine, then after about 1 minute it fails. Renewing the IP address lease (ipconfig /renew) will resolve the problem for another minute or so, but then it fails again.
I've duplicated this issue with PCs on our LAN and also over VPN. Both on PCs (Win7) and on a Mac.
Other users (the majority) don't have the problem at all. They can ping all day long to this one server w/o any problems.
The issue is, this is our Exchange server, so that's causing a bit of consternation with my users.