Thanks Dan. I had seen this earlier but my concern is that -

1 - It not occasional but an almost daily issue.

2- I have not been using Zotero for the last six months so I am unsure what long operation could be in process on a daily basis.

Thanks.

We also get almost no reports of this on Macs, so it would seem you either have a very old Mac, a very slow disk, or something else that's interfering. But if you leave Firefox open, as most Mac users do, this shouldn't be an issue.

My comments were factual, not dismissive. It's very uncommon for this to happen on a Mac, and if you want us to help you debug it you'll need to provide more information.

What is the file and line number referenced in the message? When does it occur? Is your Zotero library on a network drive? Why are you restarting Firefox to fix it?

Have you tried clicking Continue a few times? If you click Stop Script, you will break Zotero until a Firefox restart, and the next time is unlikely to be any faster.

You can also try the 2.1 Beta, which should speed up Firefox startup dramatically. But something is still awry on your system if you're getting this regularly.

Is this on a network drive?

If Firefox is becoming sluggish, there's something wrong with your Firefox installation—Firefox does not get sluggish on its own. Try disabling your other extensions. Again, most Mac users should almost never need to restart Firefox (or any application).

It doesn't respond when I click Continue.

You may need to click it multiple times, or just set that setting to a higher value (or 0) as explained on the linked page. It will almost certainly complete. Trust me.

What other extensions?

Do you have other Firefox extensions installed?

I suspect it may be Zotero that is causing the Firefox sluggishness, and my daily need to restart it.

One of the few things in Zotero that could cause this would be repeated failed auto-syncs, in which case you should see an error to the left of the sync icon in the Zotero toolbar. You can also disable auto-sync in the Sync pane of the Zotero prefs to see whether that's the case.

Is this error fixed on 2.1 Beta?

It's not an error. It's a warning from Firefox, as explained on the linked page.

The Zotero 2.1 Beta will make this less likely at Firefox startup on systems that are experiencing it. But again, those are almost always older Windows systems with very slow disk access. I can't stress enough that this is not normal behavior on a recent Mac system, and that you also should not need to restart Firefox regularly.

ijstokes: See http://www.zotero.org/support/kb/unresponsive_script_warning and the above.