unkillable process stuck in "nfsaio"

I was creating a big .iso image using mkisofs. The file was written over NFS 
to a remote share.

When I decided to stop it and pressed Ctrl-C, the process hung and remains 
unkillable (even with -9).

Pressing Ctrl-T prints the following:

load: 0.04  cmd: mkisofs 48414 [nfsaio] 0.70u 5.89s 0% 8784k

The share is mounted as:

	pandora:/backup on /tmp/.a/pandora/backup (nfs, nosuid)

The client is FreeBSD 6.1-PRERELEASE #0: Mon Mar 13 ... i386.

The server information is deliberately witheld, because it should be possible 
to abort and kill the client-side writer regardless of the server version :-)

Thanks in advance for fixing this bug. Yours,

	-mi