Hi Abbie,
Log in as host. To clear the cache, from the Host menu, choose Site Settings, expand Advanced Settings, expand Other Settings. Next to Performance Settings you'll find the Clear Cache link.
To reindex, from the Host menu, choose File Manager. Below the file manager box, find the Synchronize Database and File System link. If you have a large number of files, the operation may time out. If that hapens, you'll have to make a change to the proper setting in your web.config file.
To run a querie from within DNN, from the Host menu, choose SQL. There you can type or paste your query and execute.
Just a side thought....If you've logged in to your site under one account, then log in as another user (whether or not you log out in between), your browser still has the cookies from the other login(s) stored. Try clearing your cookies, temporary internet files, and history each time you log out. It's possibly the source of this problem.....maybe.
Good luck, Rick