I have two RHEL 7 hosts, one is supported by me and one is AWS. Firefox is the default program to view an html file, so running gio open <file>.htm should either launch firefox and display the file, or if firefox is already running, it should open the file in a new tab in the running copy of firefox. This works fine on the host supported by me. However on the AWS host, the first file will launch firefox and display, but subsequent files, launched from the same xterm, result in "Firefox is running but not responding...". I have searched and found suggestions about the profiles, so I created a new profile file that is identical to the one that works apart form the names. I found suggestions related to .parentlock, so I tried removing that. That resulted in a new browser being launched and a new .parentlock file being created, so that didn't help. Both hosts are running the same version of firefox, installed using rpm updates. I have tried the MOZ_DBUS_REMOTE and MOZ_NO_REMOTE environment variables, but they didn't help either. I looked in about:config at the various ..newwindow.. options, and those are the same between the two hosts. I did notice that opening a new tab in the browser in AWS takes longer, but I don't know if that is relevant. Any suggestions for how to have the currently running copy of firefox display multiple local html files would be appreciated.