Hey, wanted to chime in here as we're getting a redirect loop also. We're using DNN 4.9.0, Url Master, and Events 5.0.0 RC2. 

Reproducing is "simple". If you visit http://www2.tacf.org, follow steps 3,4 on the bottom right calendar (in list view).

1. Add the event module to a page
2. Add an event.
3. Click on this event, to see the detail view.
4. Now click Return. You should be throwin into a 302 redirect loop.

I've tried disabling the URL Master, but I still get the same problem. If the issue is with a malformed cookie though as mentioned above, then I suppose the issue could still manifest after the URL master is disabled, if the cookie is still present?

OK, at some point in the next few days I'll test the RC2 build that has been posted, on a new DNN install with URL Blaster.

Cheers
Roger