Can't log-in to super-admin

There is something wrong with my multi-site. I noticed after my server's customer support rep changed the upload size setting on the back-end of my site, but I am not certain that that is when the problem began.

I always sign in as the Super-Admin, but am taken to the log-in page every time I try to switch site dashboards. At that point, sometimes my user name and password works, sometimes the log-in page just reloads every time I input my username and password.

This ALWAYS happens when I try to access my network admin so that I can't update plugins, or access my wpmu dashboard - the log-in page simply reloads every time I input my user name and password.

I have tried changing the password, I have tried everything.

So I am currently unable to change settings, update plugins or access my wpmu dashboard, and often access the dashboard of any of my sites.