What could be the cause?  Logged in as host, almost all the buttons on the host file manager are disabled (no ability to sync, upload, create or delete folders, etc.) and I can't see any files or folders in the host root.  But the Admin file manager is working fine.  DNN 5.4.4. Windows 2008/IIS7.  I checked the permissions on the file system - they are correct and the same between portals\_default and the site's root folders.  Worried my host account was messed up, I made a new one, but that didn't help. 

I'm wondering if this is related to other persistent problems I'm having, like when I try to install or upgrade modules.  It will often fail when trying to replace a dll file, though new files (assemblies or not) will usually be created in the right location without issue.

Any guidance would be most appreciated.  Thanks.

Saving the host file manager's modules settings didn't do anything. 

The strange thing is that I'm logged in as host, so I'd think it would check modulepermissions - superuser access should override that?  If I look at a clean install, there aren't any permissions on the host file manager module.  But I went ahead and checked and I did find a modulepermissions row in this DNN instance:

ModulePermissionID    ModuleID    PermissionID    AllowAccess    RoleID    UserID    CreatedByUserID    CreatedOnDate    LastModifiedByUserID    LastModifiedOnDate
2292                                  323                 2                             1                         3           NULL         1                             20100720:23:42.023         1                                         2010-07-23 20:23:42.023

Yes, ModuleID 323 represents the Host File Manager.
RoleID 3 is Administrators for the portal through which I'm accessin the Host File Manager.  Technically, this shouldn't exist since the module should not be visible to Admins.  Also I'm logged in with a host account and other working portals I've seen have no ModulePermissions entry for the Host File Manager. 
File system permissions on the host root folder are correct.

I'm still at a loss...