[TYPO3] The extension list has not changed remotely, it has thus not been fetched.

[Simon Angling]

>> I had this error this morning. I raised the memory usage to 35MB in 
>> php.ini and deleted extensions.bin and extensions.xml.gz from 
>> typo3temp and then updated successfully.
> 
> If it hasn't remotely changed so why would you download it again?

Good question. In fact it was an error as the original download hadn't 
completed correctly due to the php memory limit.