Can't get access to the admin. Session is expiring

I just installed the new version of a theme which was supposed to work with W3 Total Cache but now, although I can login to the site, whenever I move to another page I get redirected to the login page and that's it.

It is a single site, using BBPress and BuddyPress.

I want to disable the cache, but I can't get access to the admin of wordpress. So I can't enable support access neither.

Thanks a lot for the help. This is really urgent :slight_frown: