Edit:- The Error Came back after re opening the editor :( will continue to search for a fix before downgrading i think. I seem to have intermittent errors when i follow the below "gears" details but not sure now.
I too have just encountered I feel i have a little more to add.
I had above mentioned problem tried refresh page, turn off super cache, open in IE8, FF3.10 both with no visual editor buttons.
I then went to the Turbo Gears setting page located in the Tools ==> tools section i had too different but confirming encounters here.
In Linux apache2 based web server the gears section did a rescan with out any real need to do anything numbers were in the red and auto scanned. I then went to edit a post and my buttons were back.
In a Windows IIS based site the gears section did not want to auto scan for me so i had to go to the tools menu in the browser i was in and disable gears i then went to edit a post and again the buttons were back. i then went back to the gears setting and enabled it again with no problems.
I study web design and regularly have problems with caching i hope this helps one person if anyone else can confirm or deny this would be great. Thanks!..
Press on lol