Not quite sure whats trying 2 access ur pc but the fact that your getting the pop ups means that your safe as the attempt to get in is being blocked. U keep getting the message as its something different everytime so hasn't been remembered by NIS. Annoying yes but at least your pcs safe.
Probably worth scanning ur pc 4 spyware / malware and virus / trojans just in case theres something nasty on your pc thats causing this 2 happen.
Other than that I think you'll have 2 wait for some1 else 2 help ya out here