When I RMB the tray icon and select “open Comodo antivirus,” nothing happens
I’m running on XP Home SP2
G’day,
Given that I can’t reproduce either of your two reported conditions on 6 PCs, I would suspect a faulty installation of CAVS. Can you please uninstall, reboot, redownload (just in case there was a problem with the original download), reinstall and reboot.
Cheers,
Ewen 
as I said in my reply to your other post, EI7 might be the cause, in my case uninstalling EI7 helped
Comodo has released the next Beta of CAVS https://forums.comodo.com/index.php/topic,7397.0.html. This thread is being locked as we move forward with this next version.
Thanks for all your help!
LM