I am also with Yahoo email. Recently, my internet provider (AT&T/Yahoo) required me to switch from Computer Associates (CA) virus protection to McAfee. Since then I have had many problems with opening attachments - PowerPoint files, photos, Adobe Acrobat (this one from a very trusted source). The file opens after about the fifth time of trying to open or save it. I contacted McAfee. However, even when they have me turn off McAfee (through Run, msconfig, stop McAfee Services) it still happens (although I'm not convinced as much). McAfee told me it was an error in my received attachment (a photo at the time which actually downloaded with no problem on my other computer protected by CA). But it is progressively getting worse (spreading to the other types of files mentioned above). I see the response above says to check the firewall and filters but check what exactly?
Just go to your attach file option in your mail box..
and then clik on this button then it will display browse button for which file you want to attach from you computer...give your targeted url for attachment...
then email browser automatically attach your file with email id..