I'm experiencing the same problem with every update since V21 was loaded.
CD will open OK if I set the 'Open new Tab' Page', but will not open if I set it to open https://www.gmail.com
or any other link.
It opens a blank white page & just sits there, says it's loading but doesn't
If I click the 'New Tab' it opens immediately!!
I have uninstalled & re-Installed CD & the Default profile several times but it hasn't solved this problem.
If I use a gmail desktop shortcut with the 'Target' = "C:\Program Files\Comodo\Dragon\dragon.exe" --app=https://mail.google.com/mail
and 'Start In' = "C:\Program Files\Comodo\Dragon"
CD hangs in the exact same way!!
Also found a solution..
Settings-->Privacy--> uncheck the Enable phishing and malware protection option.
That's a worry since CD is supposed to offer more security!!! and the solution defeats it. *sigh*