Wow- this one took a while to figure out. was editing a theme to a blog install. Was very basic- adding some text to footer file. Which I have done about 5 gazillion times- but first time with this theme. Made the changes and hit “update file” Got this error:
“The requested theme does not exist”
The name of the theme is pulled from the stylesheet. The designer had used an “&” symbol in the name of the theme- in the style sheet and no where else.
The “&” symbol is called an ampersand, btw.
Was easy to fix. Can edit cs file with an ftp client (right click on the css file on server and change name) or download onto harddrive, change and re-upload and overwrite the old file.
This was an odd one. Must have something to do with newer version of WordPress and OLD theme.