#1 - Sept. 12, 2011, 8:48 p.m.
The Diablo III development team just got back to me about a work around for this error several of you have reported.
Players should try removing their Battle.net cache folder located in their program data. The full address to the folder is here:
Note: This will ONLY fix the login issue with Error_3. You may still get the error when making heroes, deleting heroes, and starting a new game, but you should be able to log in using this work around.
Thank you guys for your patience and with your help trying this work around out. Let us know if this does not fix your Error_3 issues.