This can be a problem if you are running 2 security things at one time becouse they lock eatchother as a virus (becouse they search your comp) or other bugged system applications for example svchost.exe. try uninstalling one of the anti-viruses and/or try re-installing CA if that doesnt work then format your PC with a new opsys.
Note: first check your RAM memmory level and check how much is used with the task maneger.