You probably have a corrupt cache for the new version. Clear your
cache and cookies, this often fixes the problem, and is the first step
in the troubleshooter if you go to report a bug. You can't tell GMail
to always load the older version, but you can tell your browser.
After you click the older version link, bookmark it, that will be to
the older version. This doesn't solve your problem, only avoids it.
You need to try clearing the cache and cookies as the first (and
hopefully last) step to fixing the problem.
--
Oliver Wendell Holmes Jr. - "Lawyers spend a great deal of their time
shoveling smoke."