This occurs at Arrisi.com. Arris is Motorola's cable modem sub-company, and is the official site for info on specific Motorola and Arris modems. Sometimes pages load fine, sometimes a page gives me the message " dotDefender Blocked Your Request"
Reloading the page yields the same message, but navigating to the same page from a google search seems to work fine- i.e. page displays and no such message.
Also, sometimes pages at Tom's Hardware will give me a "Suspicious Activity Detected!" warning, and require me to enter a captcha in order to see a page.
I have Norton Security Suite, and scan fairly regularly with MBAM. I am certain my drives and OS are malware free. Is this anything to worry about?