feisty to gutsy upgrade - now cant print to network attached printer

I have a small home network consisting of 2 Win XP machines wireless connected to a router, and 2 ubuntu machines cable connected to the same router. I have a brother MFC425CN printer which is cable connected to the router ( and has its own ip address on the network). After upgrading one ubuntu PC to Gutsy, I am no longer able to print to the printer from that PC. Printing from feisty worked fine. I have de/re-installed cups, and recreated the printer through gnome print management, with no change to the behaviour. I can still print ok from an XP machine.

Wireshark network monitoring shows the gutsy pc establishes a TCP/IP session with the printer, and then disconnects the session. No frame larger than 74 bytes is transmitted...
192.168.0.100 is gutsy, 192.168.0.101 is printer - network session packets below
pkt_num time source destination
22 15.217928 192.168.0.100 192.168.0.101 TCP 32938 > 9100 [SYN] Seq=0 Len=0 MSS=1460 TSV=1238317 TSER=0 WS=6
23 15.222116 192.168.0.101 192.168.0.100 TCP 9100 > 32938 [SYN, ACK] Seq=0 Ack=1 Win=4380 Len=0 MSS=1460
24 15.222144 192.168.0.100 192.168.0.101 TCP 32938 > 9100 [ACK] Seq=1 Ack=1 Win=5840 Len=0
25 15.272086 192.168.0.100 192.168.0.101 TCP 32938 > 9100 [FIN, ACK] Seq=1 Ack=1 Win=5840 Len=0
26 15.275307 192.168.0.101 192.168.0.100 TCP [TCP ZeroWindow] 9100 > 32938 [ACK] Seq=1 Ack=2 Win=0 Len=0
27 15.320808 192.168.0.101 192.168.0.100 TCP 9100 > 32938 [FIN, PSH, ACK] Seq=1 Ack=2 Win=0 Len=0
28 15.320840 192.168.0.100 192.168.0.101 TCP 32938 > 9100 [ACK] Seq=2 Ack=2 Win=5840 Len=0

anyone got any ideas ??