Cannot attach more than three small j'peg's, at a time.

When using Firefox for my browser, and using Yahoo for my emails, I cannot attach more than three small, email sized j'peg's, at a time, or I get a "Cannot be saved, as a draft" splash screen, and the email locks up. If I attach, only three attachments, let them load, then attach additional sets, of three j'peg's, it will upload them, and, allow me to send the email. My local PC repair shop has been on my PC, and witnessed this problem. They used another browser, and used my Yahoo email a/c, without an issue - all eight photos uploaded correctly. Their decision is, that it is a Firefox problem. PS: Before the last several "new, and improved, Firefox updates, all this worked, as it has, in the past.