I have a network of WP installs @ http://thafederation.com
The visual editor works @ http://thafederation.com and other subdomains eg., http://smokingpot.thafederation.com/ & http://viztv.vizfact.com ,
But not http://yankmob.thafederation.com (which has been sterilized and is pure WP now-all plugins removed, and a prime example of why we don't fool around with WP Multi-Site).
I am unable to duplicate this problem and I would expect to have this issue network-wide, but glad I don't.
Another thing to note, is this Yank Mob site (which was running a woo theme) hasn't been maintained for months, however, other sites that haven't been maintained for months have no problems with the visual editor.
This is weird.
Its probably easier to just delete the entire Yank Mob install, and re-import the files, but seeing this problem wasn't duplicated across a network where all plugins and themes are the same baffled me.
This site: http://jroc.thafederation.com/ - is built the exact same way the YankMob site was, but the problem doesn't occur.
I thought I'd stop by and leave a note. I do need help with this issue.
I appreciate any responses.