You should be able to uninstall them from the add-on manager use

• Firefox button -> Add-ons |Extensions| [Remove]
  or keyboard keys Ctrl + Shift + A

What are the extensions ? have you tried to check for updates to them, or have you tried installing and running the compatibility reporter that sometimes gets add-ons working again.

Thanks. See, the problem is that when an addon is no longer compatible there seems to be no easy option to get rid of it, certainly not from the standard menu level. Compatibility is one thing, but it's not that I really need them, I simply want to get rid of them. The ones I mean (on FF5.0) are:

• DivX HiQ 2.1.1.94
• DivX Plus Web Player HTML5 2.1.1.94
• Firefox Synchronization Extension (from the Nokia Ovi Suite) 7.3.4.74
• HP Smart Web Printing 4.60
• Skype extension 5.3.0.7280

I think the problem will grow among other users with FF release schedule getting faster... not all developers will be able to keep up, I think.

Most or all of those extensions are probably added (installed) by other software and disabled because they are no longer compatible.
You will have to remove them via the programs that added them.

• http://kb.mozillazine.org/Uninstalling_add-ons
• http://kb.mozillazine.org/Uninstalling_toolbars

Hey cor-el, you're totally right in your reasoning. I have tried Safe-mode, but that does not allow removing inactive addons either. I guess I will have to downgrade until they are compatible, remove them then and then upgrade back to 5.0...