firefox cannot resize gmail file upload dialog

when using Gmail and I click on the attachment link to see the File Upload dialog, it is always displayed full screen and I cannot resize it. the little << thing in the lower right corner does nothing and there are no resize controls in the upper right where X is. running Gmail using Chrome does not exhibit this problem. I recently did a Firefox "refresh" and it did not change this behavior. this is a new problem that must be related to a recent change somewhere as I have not seen this problem in years of prior use of Firefox and Gmail. It just did the same thing when clicking the Browse button on this Mozilla support page -- so it is not a Gmail specific problem.