Yeah, we've been bitten by this too, around once a year, even with our fairly reliable and redundant network. It's a PITA, your process just hang and there's no way to even kill it except restarting the server.
> intr / nointr This option is provided for backward compatibility. It is ignored after kernel 2.6.25.
(IIRC when that change went in there was also some related changes to more reliably make processes blocked on a hung mount SIGKILL'able)