Here are some things I advice in such situation:
1. If there is any .htaccess file at the root of your site, check that it is correctly set.
Redirection issues may come from here.
2. In MODx Evolution > Tools > Configuration > File Manager (Tab),
check that the File manager button is set to [(base_path)]
and click the "Empty" button if it is not.
3. In MODx Evolution > Tools > Configuration > File Browser (Tab),
check that the path to the files directory is set to : [(base_path)]assets/
and click the "Empty" button if it is not.
4. Make "Site > Clear cache".
Reading the message returned, check that cached files were not only found but actually deleted.
5. If necessary, locally or in FTP, go in the "asset/cache" directory and delete the cache files, which ends with ".idx.php" (MODx will recreate them automatically).
7. If you're using Mozilla Firefox, there seem being sometimes some kind of session cache that is reluctant to deletion. Close the MODx tabs, clear the MODx cache,
close Firefox and restart it.
8. If this does not suffice, test with another browser, like Internet Explorer.
This will help knowing if the problem is browser-related or not.
9. As for the frontend of your website, also check that in your templates the <base href="
http://something.../" /> tag is set correctly.