How many add-ons do you have installed?

Seventy-seven enable and twenty-seven disabled. The number was not an issue prior to FF17.

Thanks for that information.

Some add-ons interfere with the Add-on Manager itself, causing it to open very slowly or not at all.

Can you please try opening Firefox in safe mode and then trying to open the Add-on Manager again? My bet is that the Add-on Manager will open quickly when you do this.

If the Add-on Manager does open quickly in safe mode, you might want to return to normal mode and then disable add-ons one-by-one until you find the culprit. If you have AutoPager or Tab Mix Plus, try those first, as they have been known to cause this problem in the past.

Thanks -- I'll give it a try and let you (and others) know the results.