This probably happens whenever WebAdvisor updates as that re-initiates the warning and possibly also when Firefox updates as it would reset the default search engine in some cases.
Once reset to what you want that should be the end of the warning.
Based on your description, the problem you're seeing is simply a reminder; we check with you every few months if you still want SecureSearch turned off.
If someone has turned off SecureSearch by selecting another search engine e.g. Google, then we would start the process of checking if you still want SecureSearch disabled.
Again, based on your description, it appears that this behaviour is "by design", meaning that there's nothing wrong; there are no technical problems with your McAfee WebAdvisor, or malware on your system.
i am not getting a good explanation of why secure search keep shutting off. your explanation i have seen so far all sounds like b. s. to me. is secure search a real program? are you having problems with it? i am getting very tired of this!