I wouldn't be surprised if they're dropping those packets.  Try this:
~> nslookup
> server 24.31.3.9
> mtu.net
You should get the address for mtu.net.

-- 
Jon Schewe | http://mtu.net/~jpschewe
For I am convinced that neither death nor life, neither angels 
nor demons, neither the present nor the future, nor any 
powers, neither height nor depth, nor anything else in all 
creation, will be able to separate us from the love of God that 
is in Christ Jesus our Lord. - Romans 8:38-39