I have two AS modules (welcome center for authenticated users & mini login for unauthenticated users) set to display on all pages.  However, I have noticed that on some admin pages, admin modules don't work as expected (for instance searching for a username in the user accounts page just refreshes the page).  

After I delete the AS modules from those particular pages, the pages work correctly. 

Is anyone else running into this?

Does anyone know if there's a way to "add to all pages but not on admin pages"?

I am not sure what the best option is. You can add the Welcome Center / Mini Login as a skin object. Can someone say if the skin object is the best way to implement the Welcome Center / Mini Login or is the Custom View a better method? I seem to be having browser compatibility issues with the Welcome Center / Mini Login.

I would try separating the Welcome Center and Mini Login to isolate what is causing the problem (or determine that the problem is the two together). FWIW, I'm using the Welcome Center skin object on my site and I haven't had any problems on any pages, including admin pages. I am not using the Mini Login, though.

Seems to be an issue with using either one as a module; I have removed each and still have the problem until I remove both.
I previously had the welcome center set up as a skin object, and that worked just fine. I will see if I can re-implement that and combine with the mini-login.

One option is to use a separate skin for admin pages and add it as a skin object that you can use for non-admin pages.