There is a new problem with XfinityConnect and the ability to add attachments. The Comcast team has been notified of this issue by the Administrator.
You can try switching to the Lite version of XC and see if that will work for you.
To do: Open XfinityConnect, click on Preferences>General. In the windw that opens, check the box for the Lite version. Close and re-open XC. Now try to add an attachment to an email.
Let us know if that helped or not.
Need Email Help? Please post the following information in your post. Do you use XfinityConnect? The Full or Lite version? Do you use an email client? Which one? (Eg; Windows Live mail, Outlook, a smartphone etc.) Which browser/version do you use? And- have you cleared your browser cache? Which operating system? XP, Vista, Windows 7, Mac OS X Details of the problem you are having.