It is extremely difficult to determine whether redirects and pop-ups are related to ads that have snuck through the system or if it is local malware. This can reside in a browser addon/plugin, in the OS or even in some home routers and often not detected by the most popular malware scans as I have learned.
Making it even worse is that usually I can't replicate the issue even with hundreds of reloads and they often only happen to a very small number of people, possibly because they were targeted based on location or browsing history or because indeed they did get some malware.
When I start getting multiple reports of the same issue across different platforms/browsers, then it becomes more likely to be related to ad networks. Even with 1 report, I'm usually happy to place a block if I have enough information and it is an obscure company. For more legitimate companies, I prefer to have multiple reports. Plus, it's also helpful to know that no other tabs/windows were open, as pop-ups and pop-unders can be served by others too.
For example, right now there is a case of phony Amazon ads running through at least one network. It looks like an Amazon ad, but leads to a malicious website. Nice, right?
Heather, was it the exact same pop up that appeared on both the blog and the forum? That reduces the chance of something on your system, but not completely eliminates it. If you see it again, can you see if there is another ad in common on the page or perhaps see what URL it takes you to? Then I can at least implement a block, since it may not be FTD.com...
