[TYPO3-english] Help: I get trapped in upload-action

[Santiago]

Hello,

I installed typo3-4.4.4 and the 4.5-alpha3 and with both releases I get 
trapped in the upload-action from file->filelist - fileadmin - "Upload Files".

When I start that action, the screen gets dark and a panel "File Upload 
Progress" appears - but within that panel, I can't select a file to upload, nor 
can I cancel the action to get back to the BE-interface.

I'm new to typo3 and I use debian squeeze with the t3-packages from sf.net 
(not the debian packages) for the BE and debian squeeze/iceweasel for the FE. 
I followed the instructions from INSTALL.txt - but may be I missed something.

Any hint is welcome.

cheers Santiago

P.S. If anybody can tell me, how I can enable the introduction 
extension/package, it will be very appreciated. I see the extension has state 
'installed', but the database is stil empty, so I think, I need to do a kind 
of import. But I don't know what and where ...
The manual of the introduction package does not tell me much about it.