The first time I started my new nightly the download panel icon appeared after a few seconds. Clicking it hung my browser for a short time but eventually showed the panel with all my recent downloads. After a restart the icon just doesn't show up in my toolbar at all. Clicking downloads in the firefox menu makes the icon appear and the panel show, but it's empty aside from the link to see all my downloads in the history manager.

Something permanently applies [collapsed="true"] attribute. This attribute causes the style from firefox/omni.ja!/chrome/toolkit/content/global/xul.css (Line 35) to work out: /* hide the content, but don't destroy the frames */ [collapsed="true"], [moz-collapsed="true"] { visibility: collapse; } So as a temporary fix you may apply this style: #downloads-button { visibility: visible !important; } But this is a temporary fix, we need to understand why this attribute gets set to fix this issue completely.

Is this the same as bug 746591?

this bug refers to the old behavior, so it's invalid as of now.