When I log in using the host account I can't see or edit the text in any text/html modules. If I'm not logged in or if I log in as an admin I can see the text fine.

The only thing I can think of that might have caused this is that I installed a new module called DNNsitemap an hour or two before this problem started, so I uninstalled it, but this didn't fix the problem.

Does anyone have any idea why this would happen or any suggestions on how to fix it?

Would an application restart erase all the content and pages on the site? Or does it just clear caches and do stuff like that?

There could be a lot of reasons for this but one reason that I know causes it are certain CSS/Javascript combinations. We use the SIPHR tool to use custom fonts on our titles and for some reason they don't show in Admin mode. I'm not sure if its caused by differences in admin caching, skin generation order or what. It's annoying but not a dealbreaker for us. Does it still happen to you if you drop back to one of the stock DNN skins?