Yea sorry I vanished for a little bit somebody got there already. Scanning with SuperAntiSpyware and Malwarebytes would be best. I've also had good experiences with the ESET online scanner, it works well and isn't very well known. Though last I checked it picks up DFHack's fake SDL.dll as a false positive.
I suppose it's possible it was just ISP funkyness. But a good detailed scan now and then doesn't hurt, and that behavior you described would certainly be enough for me to have run scans.
Note for in case it isn't apparent: Having a well known scanner isn't necessarily a good thing, if your anti-malware program is well known, folks who write malware are more likely to write their virus to hide from or disable it. While bigger companies have the resources to counter that, it ends up being a big game of cat and mouse.
Malwarebytes picked up nothing after a full system scan O_o
I'll try ESET, though it'll probably give me problems as I have several copies of DFHack on my system

I'll also attempt a rootkit scan, though if that still turns up nothing I'll have to concede it was ISP shenanigans.