Here is the support article from Anet on this issue -
http://support.plaync.com/cgi-bin/pl...p?p_faqid=3104
It could be the ports are blocked via Firewall / Security software (or router settings). You could have that Netgear router they mention.
They have a utility to run that generates a log file to let you know if it's being blocked from talking to there servers.
If it worked then stopped after an update pushed from guild wars. Un-install guildwars, then re-install it. Sometimes the update corrupts the data file messing up gw.