That isn't really great to hear. You shouldn't have to re-install software to fix a problem, especially not scripted software.
The problem I had with this was as follows:
Built modx on my Ubuntu laptop.
All working.
Migrated it to a CentOS server
File Manager stopped working
Problem was that PHP installation on laptop had PHP mbstring module, but server did not. This is used by file manager browser.
Ran yum install php-mbstring on server
Restarted apache
Problem fixed
