Hello,
I had this problem also. I just set up a new laptop w/Vista Home Premium and the virus update would not work. I followed this advice from another poster and it worked for me:
"I did this solution and I was able to update the virus definition too.
Go to Control Panel -> Admin tools -> Services
Search for "COMODO Internet Security Helper Service" and edit properties.
In Start Sesion change the "Local System" option to your loggin account.
Apply -> Accept -> Restart your system.
Thats All...
I was tryng with different options:
With Local System option: I wasn't able to update the virus definition.
With Local Service Account: Error Code 0x800705aa - insufficient system resources exist to complete the requested service.
With my Loggin Account: Success, I was able to update.
I don't know why the Local System option doesn't update and the Loggin Account does."
This link will lead you to a large thread on this topic. I have read that this is a known issue and will be fixed with the next version release.
http://forums.comodo.com/anti_virus_bugs/cant_update_virus_database_cis_3555810432_merged_threads-t29013.60.html Good luck.