issue getting response from some gtld servers

[Will Yardley]

I'm noticing a weird problem with bind9 dig... bind 8 dig seems to work
fine.

aura% dig @a.gtld-servers.net net. soa

; <<>> DiG 9.2.3rc3 <<>> @a.gtld-servers.net net. soa
;; global options:  printcmd
;; connection timed out; no servers could be reached

My system seems to be resolving a.gtld-servers.net itself just fine:
aura% dig a.gtld-servers.net +sh      
192.5.6.30

Digging at that IP works fine:

aura% dig @192.5.6.30 net. soa +sh    
a.gtld-servers.net. nstld.verisign-grs.com. 1100265444 1800 900 604800
900

I get the same problem with b.gtld-servers.net; others I checked (e, f,
d) seem to be fine.

On the same machine, bind 8 dig works fine:
aura% dig.old @a.gtld-servers.net net. soa      

; <<>> DiG 8.3 <<>> @a.gtld-servers.net net. soa 
; (1 server found)
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 13, ADDITIONAL: 11
;; QUERY SECTION:
;;      net, type = SOA, class = IN

;; ANSWER SECTION:
net.                    2D IN SOA       a.gtld-servers.net. nstld.verisign-grs.com. (

On another machine (on a different network), bind 9 dig shows the same
thing.