Great - like you Christiaan, deactivating all the plugins allowed me to re-install the upgrade on one of my two websites. Now I have the toolbar icons working in Visual Edit - and things seem to work.
After upgrading to 2.8 on my other website, all the Visual Edit toolbars appeared fine but when I tried to upload an image it did not appear.
I have tried upgrading Auotomatically with this site, which is with Hostpapa and got a Fatal Error Message saying that the 'Allowed memory of 33554432 bytes was exhausted. Tried to allocate 2348617 bytes in....'
I can't imagine that there should be a limit with Hostpapa.
Any ideas anyone?
What a nightmare - thank you so very much for all the help that's flying around. I would have been totally lost without it.