nextgen gallery issues — please help!

I am using Firefox as a browser, trying to insert a nextgen gallery into one of my pages, and it is not working. I click on my Gallery page, Edit, and click on the “Upload/Insert” media file button. I click on the NextGen Gallery tab, and then select the gallery I have pre-made, then click “Select.” Then all the photos in that gallery appear below. I click on “Save Changes” and the mouse looks like it thinks and then stops, and NOTHING CHANGES. I wait and wait, nothing happens. So I click the “X” box in the upper right hand corner, and nothing has been inserted. This is so dumb. Somebody help me.