sendto: no buffer space available (yet no queue and plenty mbufs)

[Christoffer Pio]

I'm experiencing the em intel nic 100/1000 mb driver produces the
'no buffer space available' error when I break the connection (pull out
the cable), yet netstat -m and netstat -an shows no packets in queue
and plenty of mbuf and nmbclusters free. When I plug the cable back in
ping resumes shortly working alright .. 

It must be the buffer on the NIC which gets exhausted? I am trying to make sure
it is safe to put the box into production environment, the em driver is not
buggy on freebsd 4.8 ?

Christoffer