From the SandboxIE forum --Tzuk (the developer) said…
"I downloaded Comodo Firewall from the link in the first post, and I got COMODO Firewall version 5.0.163652.1142 which seems to be more recent than the version reported at the top post, version 5.0.162636.1135. – On Windows XP SP3, I’m not seeing any conflicts or problems…
Not really sure what to tell you. I installed COMODO onto my test system (which even already had AVG installed as I was looking into another problem) and then restarted the computer and I tried Run Any Program and Run Web Browser in Sandboxie and both worked fine with no error messages."
Maybe you should just make a system restore point and then completely de-install your old version of Comodo and then install Sandboxie and then Comodo.
If there’s a conflict you can always run a restore.