During the maintenance period we did a purge of all the millions of house levels.
Since houses are all based on templates and the furniture is stored in a separate database this isn't an issue but will cause your house or guild house to be unavailable for other people to visit until you enter your house or guild house at least once.
We plan on putting in a fix to make it no longer necessary to enter your house at least once for others to visit but it likely won't be implemented until after Christmas.