Mozapps script causing my downloads to freeze

Question

When I am downloading files the download just stops (about 85% of the time), the page glazes over and the top shows "Firefox not responding); all open Firefox windows freeze. After some time (several minutes) a popup appears stating that a script is not responding and shows script details: chrome:/mozapps/content/downloads/downloads.js.1222. It also gives the option to wait or cancel the script. When i cancel the page returns to normal and download starts again; other Firefox windows also respond again. This has only started in the last several days.

Answer 1

I have had this same problem for a couple of months. It doesn't happen all the time but seems to happen the first time I download something after rebooting.
I downloaded download.js and What I see at line 1222 is:
// Because of the joys of XBL, we can't update the buttons until the
// download object is in the document.
updateButtons(item);
Am I getting a newer version or something?
The complete code that decides to call updateButtons is this:
// Make the item and add it to the end if it's active or matches the search
let item = createDownloadItem(attrs);
if (item && (isActive || downloadMatchesSearch(item))) {
// Add item to the end
gDownloadsView.appendChild(item);
// Because of the joys of XBL, we can't update the buttons until the
// download object is in the document.
updateButtons(item);
} else {
// We didn't add an item, so bump up the number of items to process, but
// not a whole number so that we eventually do pause for a chunk break
aNumItems += .9;
} catch (e) {
// Something went wrong when stepping or getting values, so clear and quit
gStmt.reset();
return;
So it seems to be getting stuck when adding the new download to the list of downloads. I cleared my download history so I will see if that fixes it and post here if it did.