3.3. Users who use the products with version 6.3:
If you are using 6.3, your products are fully compatible and certified for Windows 8.1 already. However, Windows 8.1 upgrade has a bug that causes data loss by deleting a critical registry key used by the products(HKEY_LOCAL_MACHINE\SYSTEM\software\Comodo). Windows 8.1 upgrade is coming from a trusted source hence the self-defense in the products do NOT block the damage causing them to dysfunction. We are in touch with Microsoft for further resolution of this issue however we have also issued a path this weekend to ameliorate the damage caused by the upgrade process.
The Symptoms
Symptom: If you are using the products 6.3.294583.2937, your products will not start and you may not be able to uinstall neither.
Fix: Please run diagnostics tool by executing the command, "C:\Program Files\COMODO\COMODO Internet Security\cis.exe --diagnoseUI", when done, restart your computer. The products should be functional however your configuration settings will not be able to be recovered automatically.
I am having the same problems as others here have posted on my own 8-newly-updated-to-8.1 system. I had Comodo Firewall 6.3 installed in 8.0 (64 bit Pro version). After installing 8.1, Comodo stopped starting up and showed no icon on the taskbar. I decided to reinstall Comodo (uninstall, reboot, install), which did not work properly. The icon now appears, but with an X through it, and the error "the network firewall is not functioning properly" appears when I hover over the icon. The diagnose utility reported errors after trying to fix the problem after getting 65% through. It stated "Diagnostics have found some errors and could not fix them automatically." So I uninstalled again, rebooted, ran CCleaner's registry cleanup utility this time, manually inspected the Program Files and Program Files (x86) folders, along with the three folders in Users/AppData/, to make sure all Comodo files were removed, then reinstalled Comodo again. Same problem - an X appears in the Comodo taskbar icon, and the "network firewall" error persists, as do the Diagnostics results.
?!? Not sure what else I can do here to get Comodo working on my 8.1 machine, other than a wipe and reinstall of the entire OS etc. perhaps. I imagine that must be the problem since I have made certain no files were left on the C drive (in the usual locations, at least... I'm not sure about which dll's in the Windows folder to look for that Comodo may use, or which of those are shared with other programs). I will try that CIS cleanup tool next, hope that works...