Here's what I do every couple of days:
Go to the site - logo is missing.
![Example](http://dotnetnuke.ru/Temp/Files_Example/01_.png)
Log in as site admin.
![Example](http://dotnetnuke.ru/Temp/Files_Example/02_.png)
Go to site settings. What do you know - I don't have access to the files.
![Example](http://dotnetnuke.ru/Temp/Files_Example/03_.png)
So I go to the file manager. Noone has access but admin. Lucky for me this admin is none other than me.
(Sometimes there are no files listed there so I have to resync the filesystem manually (several times in a row)).
![Example](http://dotnetnuke.ru/Temp/Files_Example/04_.png)
I allow access to everyone and save.
![Example](http://dotnetnuke.ru/Temp/Files_Example/05_.png)
I return to site settings. This time I have access to the files. No file for logo is currently selected (it's always this way at this stage).
![Example](http://dotnetnuke.ru/Temp/Files_Example/06_.png)
I select proper image from the list and save.
![Example](http://dotnetnuke.ru/Temp/Files_Example/07_.png)
After this the logo is displayed again. For another two days.
![Example](http://dotnetnuke.ru/Temp/Files_Example/08_.png)
Keep in mind that there are othe sites in this instance of the platform. The logo disappers on them too. And only admin user can fix it. Even though I'm this admin, admin's username and password are different for every site. So I have to do this again the number of times being equal to the number of sites I have minus one. It's starting to bore me... :(
Ok, I ran out of patience and hardcoded logo into the skins. :)