Double underlined words appearing w/ hypertext, computer slow, "unusual traffic"

Just yesterday when I was viewing a message forum, random words on the page started being underlined in green with a hyperlink and when I ran the pointer over it an ad appeared like in a word balloon shape. I tried to Google the issue and got this back from my Chrome browser instead of the results:

systems have detected unusual traffic from your computer network. This page checks to see if it’s really you sending the requests, and not a robot.

I had to type in one of those words that matches the picture before I could get results.
This is only happening in Google Chrome and not in Firefox. I have Windows 7 OS. Also, my computer has been running slower as of yesterday and it takes my computer a lot more time to get a webpage or even load a program or open a file. If anyone can help I’d appreciate it. Thanks.

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