Sorry, Unable to process request at this time — error 999.
Unfortunately we are unable to process your request at this time. This error is usually temporary. Please try again later.
If you continue to experience this error, it may be caused by one of the following:
You may want to scan your system for spyware and viruses, as they may interfere with your ability to connect to Yahoo!. For detailed information on spyware and virus protection, please visit the Yahoo! Security Center.
This problem may be due to unusual network activity coming from your Internet Service Provider. We recommend that you report this problem to them.
While this error is usually temporary, if it continues and the above solutions don’t resolve your problem, please let us know.
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Please try Yahoo! Help Central if you need more assistance.

It means your computer is infected with viruses and possible spyware and Yahoo will not let you connect….download and scan with these 2 free utilities….Malwarebytes will ask you for a free trial to the paid pro version…just click on “no thanks”…the free version works just as well……..http://download.cnet.com/Malwarebytes-An…http://download.cnet.com/SuperAntiSpywar…
And if you don’t have a antivirus product on the computer…here is a free one…….http://download.cnet.com/Avast-Free-Anti…