Accepting the Terms of Service doesn't appear to work

(Bug, Closed -> Fixed, Priority: High, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Users and Identity
Summary: Discovered by Heather when she tried to sign up: she repeatedly tried to accept the Terms of Service, but it didn't work.
This turns out to be a caching problem: the accept is taking, but it's not updating the (relatively new) User Cache, so we wind up in a loop. It finally lets you in only after the system reboots and the cache clears.