Build Identifier: http://hg.mozilla.org/mozilla-central/rev/2e70b718903a Mozilla/5.0 (Windows NT 6.1; WOW64; rv:20.0) Gecko/20121218 Firefox/20.0 ID:20121218030803 Steps to Reproduce: 1. Start Nightly with clean new profile 2. Download a file (ex. http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-mozilla-central/firefox-20.0a1.en-US.win32.installer-stub.exe ) 3. Click download toolbar button to open Download panel 4. Click "firefox-20.0a1.en-US.win32.installer-stub.exe" to open it Actual results: Nothing happens And the following error in Error Console: Error: [Exception... "'Error: aOwnerWindow must be a dom-window object' when calling method: [nsIRunnable::run]" nsresult: "0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)" location: "native frame :: <unknown filename> :: <TOP_LEVEL> :: line 0" data: no] Expected reults: Downloaded file should be open. Regression window(m-c) Good: http://hg.mozilla.org/mozilla-central/rev/c8a1314aa449 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:20.0) Gecko/20121216 Firefox/20.0 ID:20121216030851 Bad: http://hg.mozilla.org/mozilla-central/rev/ba26dc1c6267 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:20.0) Gecko/20121217 Firefox/20.0 ID:20121217054022 Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=c8a1314aa449&tochange=ba26dc1c6267 Regression window(m-i) Good: http://hg.mozilla.org/integration/mozilla-inbound/rev/89f1723f42f7 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:20.0) Gecko/20121216 Firefox/20.0 ID:20121216233021 Bad: http://hg.mozilla.org/integration/mozilla-inbound/rev/38b71336dff4 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:20.0) Gecko/20121216 Firefox/20.0 ID:20121216233921 Pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=89f1723f42f7&tochange=38b71336dff4 Suspected: Bug 675902