Fire up the SQL interface (for example "mysql -u username" etc.), select/specify/set the correct database and tell the system to execute the following: "delete from ezsession;"
I ran into this same problem yesterday after moving my 3.2.4 site to a new server. I cleared the ezsession table, and that fixed it. Thanks for the easy fix, a few months ago when this happened we spent a lot of time trying to figure out why...