Latest Security patch. either refurbished 811493 or Q815021 for XP has a problem according to vnunet.com posted on 29th May. It knocks off network connection if you have symantec firewall. I got knocked off the other day after downloading one of these patches and had to spend 50p minute helpline to get reconnected.
On the vnunet site I couldn't work out which one of above patches it was so I can uninstall to prevent re-occurrence of prob. Microsoft are working on replacement patch. (This is a new problem).:(