Well, thanks for these answsers, but the real setup is one of an NFS service failing over to another let's say cluster node, where it will be started over the same IP... It's expected behaviour that it happens at the worst possilbe time ;)
Also check the NFS mount options: The NFS client code should be able to block your write attempt until the NFS server goes online again. This will make your programm stall for that time, but should do no other harm.
I'll have to check what options I have, but i'd expected default mount options to behave like that, ie stall but not lose data :/