Why Does My Anti-virus Software Keep Popping Up Constantly Telling Me All Threats Are Resolved?

I have Trend Micro Titanium Internet Security, and it’s worked great for the past six months, and every once in awhile it would pop up with a message say “All threats resolved” and then give me the number.
But this past week it keeps constantly popping up saying the threats are resolved, and the number seems to grow every time it pops up.
I’ve done a full scan, and it hasn’t found anything, but apparently I still have threats on my computer?
Does anyone know why this is happening, or how I can fix it?