.... another odd thing that kept happening earlier in the evening: I kept getting an IE message box telling me something like:
"Internet Explorer cannot open the internet site able2know, etc, etc ... operation aborted" each time I tried to access a new thread. Then, with a bit of tinkering, I'd get in each time. Weird.
That may well have been some problem at my end, but combined with the pop-ups, I thought something was definitely going haywire with my computer. Everything's back to normal now, though.