infected with adnxs?

[NutherStamper]

I hope I'm doing this correctly. Last week I updated Java and Adobe flash on the desktop computer and shortly after that I started getting adnxs pop-ups. I updated Adobe flash on my laptop as well (same day as desktop) and today I got a adnxs pop up on the laptop. I think both might be infected although it does not pop up all the time. MS Security Essentials found a Trojan virus on the desktop and quarantined it (but it got deleted before I could see which virus it was). On the desktop I ran Adware cleaner and what does pop up (Viewpoint is one thing and is necessary for our AOL software to display properly) doesn't seem like anything weird. Ran Malwarebytes multiple times (also in safe mode) and it found nothing.(this is on the desktop) Also ran MS Malicious software tool and it too found nothing. We can go days without this thing popping up, no rhyme or reason to it. I understand this ad/malware can be dangerous so how do I proceed to find this thing and get rid of it. By the way I checked in add/remove programs and the only new thing showing up as added recently is the Adobe flash, MS Security Essentials updates and Java (desktop).
What do I do first? Thanks for any help you can give me.

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