Sliders not working with latest firefox

[nveinsti]

After the latest firefox (18.0) update we now are getting a mootools error and the sliders are all fully open.

Timestamp: 28/01/2013 11:09:48 AM
Error: TypeError: c is null
Source File: http://xxx/plugins/system/mtupgrade/mootools.js [nofollow]
Line: 1

If I disable the mootools plugin it works but this is needed for other parts of the site.

Safari, IE9 and Chrome seem to show fine. Anyone else having this issue or any ideas on how to fix it?

[Dobos]

Wow, thanks for your post, I was wondering what was going on.  I am just going with disabling mootools for now and watch and see what will happen with the next firefox version.