The solution is to use a new profile for each instance. So if you want to have 10 Ui.vision instances working at the same time, you need to create 10 different Chrome profiles. For Firefox it works the same.
Once you have the profiles, you use a different one in each command line:
“C:\Program Files (x86)\Google\Chrome\Application\chrome.exe” –profile-directory=Default “file:///D:/test/ui.vision.html?macro=demotest&direct=1&close=1&savelog=log1.txt”
Chrome:
--profile-directory=Default
--profile-directory="Profile 1"
--profile-directory="Profile 2"
...
For more details see here.
Firefox:
How to create profiles:
http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
Command line: -P "profile_name"