TYPO3: Red question marks instead of language flags

You just upgraded to TYPO3 4.5.x and the backend now shows white question marks in a red circle where you used to see a language flag of the default language of your content elements? 

Since v4.5 the TYPO3 backend makes heavy use of sprites. These sprites replace all the tiny icon images that up to now flooded the backend and created hundreds of HTTP requests for each single page to load. Instead all these icons are now compiled into larger images in which single icons are addressed through CSS formatting rules. So for hundreds of different icons the backend will only load one single image file!

The flag icons have been replaced by this sprite technique too. As a result you have to change your TS-Config code a bit and delete the “.gif” part in the value of the defaultLanguageFlag property.

Old TS-Config before v4.5:

mod.SHARED{
  defaultLanguageFlag = gb.gif
  defaultLanguageLabel = English
}

New TS-Config since v4.5:

mod.SHARED{
  defaultLanguageFlag = gb
  defaultLanguageLabel = English
}