Any zone with housing or with access to housing may not be loading at this time (eg. South or North Qeynos, any of the city villages, etc). Antonica and the Commonlands should not be affected as they lead to Guildhalls.
The team is fixing this and should be putting the fix in today.
We're sorry for any inconvenience and will let you know when this issue has been resolved.
Update! Kiara has since posted:
The zoning problem should be all fixed now.
Please note that if you have a character who hasn't zoned into their house in six months, they will not be able to return home until tomorrow 
source: Official EQII forums