cannot download yahoo mail attachments


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My husband and I both use MacBooks. Nothing has changed that I am aware of. Recently, we stopped being able to download Yahoo mail attachments (pdf files). Help! We do not run Avast or any other virus scan protection. Absolutely nothing has changed for us. I have tried clearing history and cookies and going back to the site, but still nothing downloads. Nada. I cannot get an answer from yahoo or ATT. I get referred back and forth between both, lots of finger pointing, but no solutions. Why is there a problem now that was not here before? Most of all, HOW DO I GET MY STUFF DOWNLOADED AGAIN?

Just today, I was unable to download a new application for my MacBook from the Apple Mac Store. Weird.

Thanks in advance,