This subject was raised on Computer Issues a couple of months or so ago and the reply was as follows.
"Flash is a plug-in that is used to display multimedia content, like some animated menu systems or small movies or games.
It's harmless, free and is pretty much required for 'normal' internet browsing now."
It appears that it is a requirement for some of the animated banner advertisements we see on these forums. Flash has probably detected that you have an outdated version and this is why you are getting the pop ups.
I had the same problem myself a while back, downloaded the new version in a few seconds and no more trouble.