I wouldn't expect that there are issues with running the regular version and the portable version at the same time as both use a different profile folder. Can you attach a screenshot? *https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem *use a compressed image type like PNG or JPG to save the screenshot What error do you get ? Does it make a difference in what order you start them ? You can try to add the <b>-no-remote</b> switch to the command-line of the regular (desktop) version.