User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.84 Safari/534.13 Build Identifier: Mozilla/5.0 (Windows NT 5.1; rv:2.0b12pre) Gecko/20110209 Firefox/4.0b12pre If I drag and drop a button on the Customize Toolbar window it doesn't appear automatically Reproducible: Always Steps to Reproduce: 1. Open the Customize toolbar feature View->Toolbar->Customize.. 2. Scroll down to the end of the list 3. Drag and drop a button on the Customize toolbar Actual Results: The Button doesn't appear in the Customize Toolbar window The button appears only after I make a scroll or a click Expected Results: The Button should appear in the customize toolbox

Confirmed on Mozilla/5.0 (Windows NT 6.1; rv:2.0b12pre) Gecko/20110209 Firefox/4.0b12pre and Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b12pre) Gecko/20110209 Firefox/4.0b12pre

Regression Window: Works: http://hg.mozilla.org/mozilla-central/rev/16cc18d74a8c Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b12pre) Gecko/20110205 Firefox/4.0b12pre ID:20110206175132 Fails:: http://hg.mozilla.org/mozilla-central/rev/4c62984f12d1 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b12pre) Gecko/20110207 Firefox/4.0b12pre ID:20110207030345 Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=16cc18d74a8c&tochange=4c62984f12d1

I haven't managed to reproduce this with 100% reliability, but I am fairly sure it is fixed by the patch for bug 632379

Can you retest?

I cannot reproduced any more. http://hg.mozilla.org/mozilla-central/rev/51702867d932 fixed this.