Can I have TWO version od FileMan on my server, For 2 different Clients

I am a small webhosting company and already have one version of Fileman on my server for one client.  Will there be a problem if I install another copy for another client?  I dont want an admin from one to get into other... I'm guessing this will not be a problem, but I thought I'd ask first

I just tried, and the regular install does not allow it... is there a way to configure it to use two different FileVisita licences... on different websites on the same server

The installer will not allow you to install a second instance but you can always install a new instance by using the manual method:
- Extract the "FileVista" subfolder from the distribution zip package.
- Upload this subfolder to the target web server via FTP. 
- Create an IIS Application for this folder in your hosting control panel. If you don't have 
this option, request your hosting company/server administrator to do this for you. 

So the most important thing is setting FileVista folder as an Application in IIS manager.
Then you will be able to run the FileVista configuration wizard to finish the installation.