Then, suddenly, I'm getting pop-up ads 'til hell won't have it. Then I get pop-up ads for stuff like "PC-Cleaner" and "Registry Fix" and warnings that my computer is running slow and I should buy their gizmo program that would fix it.

Suspicious, I "X-ed" them off. Some of them wouldn't go away, and I had to do a computer restart.

Some of which didn't ask me, they just started to download the bloody program!

Don, if you get a popup you shouldn't "x" it with the x on the corner of the screen that popped up, you should open the task manager and close it from there. Often times that X has been doctored so it is actually like hitting return, it looks like you accepting the download of malware. There may be something at Mudcat that isn't playing well with your browser, but it sounds like when you hit X you inoculated yourself with a problem. See if you can download and install Malwarebytes/ and scan and remove the problem. You may have to use safe mode and rename the download file to trick malware.

SRS