[TYPO3] TYPO3 Element Browser: Strange Behaviour in 4.0.1 on file upload

[Christoph Roth]

Hi folks,

after upgrading from TYPO3 4.0 to 4.0.1 I encounter a strange behaviour 
using the element browser. If I try to upload an image file into a 
folder, after clicking "Upload" the element browser shows me an error 
message: "Error 2, No file was uploaded". This is always reported twice. 
  Then I have to click on "continue". In spite of these messages, the 
file has been uploaded correctly. I find it in the thumbnail list and 
can select it as if nothing had happened.

So this seems not to be severe but it is quite urgent, because most of 
our backend users get confused on the error messages.

Could this be a bug? System is running PHP4.4.2, MySQL 4.0.20

All the best,

Christoph