Unusual Traffic Captcha Not Working

Out of nowhere I got this error message when doing a google search:Our 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. It's very strange. I think it's something specific to my desktop computer like a virus or malware as the other computers on my home network don't get this. When it's on this error page it allows me to continue my search provided that I enter a CAPTCHA text and when I do, it won't accept it. I can try it 100 times and it never accepts what I type in. Any ideas? I've cleaned my system out pretty good with Spybot Search & Destroy and it's still having this problem. -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.