I rebuilt the page it was pointing to, updated the nav menu, and now it seems to work. Something went very wrong with the page it used to live on (I can't find it in the page list, but I can find reference to it in other places that talk about pages... very odd).
Support Forum
Unable to Edit User Profiles (redirected to main forum page)
so the profile stuff working now too?
Seems to be. Super weird considering we didn't touch anything to do with these pages.