Greetings,
I also recently installed Comodo. Things worked OK for a while and then I started getting the 0x5 errors too. No BOINC work was being performed. I searched the Comodo forum for BOINC and found what seems to be a solution. It goes like this:
Open the Comodo window and select [Defense +];
Select [Advanced];
Select [Computer Security Policy];
Select the line with boinc.exe then [Edit ...] (I think BOINC needs to be running for it to appear in this list);
Select "Use a Predefined Policy" & set to Installer or Updater;
Click Apply & then Apply on the Computer Security Policy page also.
I then clicked [Reset Projects] in the BOINC manager followed by [Advanced] [Do network communication].
The tasks (2) that had previously errored out were downloaded again and one of them started running. I just did this (20 May / 11:30 PM) so not sure if this is the final answer.
Hope this helps.
Best wishes,
5ftnothing