buffer overflow attack.

Today I shut down windows firewall knowingly as firewall in Comodo Internet Security installed in my computer protects from most of online threats and also thinking that running two firewalls might conflict with eachother. From that point whenever I connect my system to internet, the Defense+ shows me alert with red color(seems to be of high intensity) that it has stopped a service ‘svchost.exe’ temporarily because the service has been trying to inject shellcode and also due to memory buffer overflow attack. The Defense+ also gives me options to terminate the service or skip the alert recommending me to terminate. As soon as i choose the option ‘terminate’, all running processes in my system get struck and totally my system hangs and I have to restart my system. This has been everytime I connect to internet for a few minutes. Please help me in this regard.