Just switched off adblock plus and logged in . No extra adds or pop ups I'm afraid , only the ads down right hand side , John's Cross etc. Have you been on Asda site recently ? A few weeks ago I received numerous emails informing me "you've won......", some of them were purportedly from Argos and Asda , deleted without opening. Can only suggest running your anti virus and any other security programs on your machine. I know this will sound crazy , but I hope the anti virus finds some thing and you can delete it .
Another adblocker for the future is adnauseum , it stops them opening and you can actually see what has failed to be shown , you can then delete the "vault" they are sent to. Sounds unclear when I read it back , but when you see it , it becomes clear.
I hope you find the solution via a virus scan. A free antivirus is Avast , just google Avast and download the free version.
Try clearing all your cookies and browsing history in your browser.
It may not automatically log you back in to your websites that you normally log into automatically, but first time back after logging in manually, future automatic logins should be fine. (that's how it works on Apple safari anyhow). Make sure you know all your passwords and user names for your websites / forums
Google "clear cookies <browser name>" and "clear browsing history<browser name>" for details of how to do it with the browser you are using.