I think they said if you change your BNet location back to Azeroth/Northrend/Kalimdor/Lordaeron, you will automatically re-download the previous patch when you try to connect since those locations don't support the new patch.
If you can't connect to BNet at all (meaning you can't go to the other servers and download the old patch), I think the Battle.net site has downloadable versions of the patches.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.