[TYPO3] import extensions does not work

[Albert Dekker]

Hi List,
I have a typo3 v4 installation on a local server. For some odd reason 
the extension list is not updated:

"The extension list has not changed remotely, it has thus not been fetched."
I have seen however that the list has changed remotely (e.g. Templavoila 
has been updated to 1.1.0.

Another installation on a remote server does the update of the extension 
list perfectly and I can see the new TV extension. What can be wrong?

Regards,
Albert