[TYPO3-english] TYPO3 6.1 no thumbs in backend - but everything ok in install tool?

[horace grant]

hi,

i am using TYPO3 6.1 and don't get any thumbnails displayed in the backend.

the strange thing is: the image tests in the install tool work without any
problems.

what could be the reason for this?

cheers,
horace