Some files corrupted after upload. Unwanted conversion of word, odt and jpeg files to zip / gzip

@johanneshahn: please consider also my private message to you about this issue.

File Framework and Bitcache were running smoothly when this problem occured:

Uploaded doc, docx, odt or jpg files cannot be opened after downloading them from the file node page. Neither Open Office nor Gimp (in case of an image file) can open the files. PDF files are working.

I tested this on two different computers with different software and all the files were working before uploading them with FF.

When I look into the bitstreams (admin/content/bitcache/list) I see that there are no jpg or msword files listed, only

application/x-gzip; charset=binary
application/zip; charset=binary
application/pdf; charset=binary

I have disabled the "converter" module which is part of File Framework.

In the Drupal logs it says that it has created a "application/zip" preview f.e. test4.doc with the bitcache bitcache://0df98d5b32523073e78fbcde1...

Why does it convert the file instead of just uploading the .doc into a bitstream? Why does this not happen to pdf files but only to doc and jpg?

The stream is definitely corrupted because I cannot open a downloaded file with zip or gzip utilities.

Versions:
The problem appeared with the 6.x-1.3+9-dev version and did not dissapear after updating to 6.x-1.4.

Thank you in advance for your help!