Reply function for comments doesn’t work

Hi all

I’m facing several problems with wordpress 2.9.2. at the moment:

– Reply on comments doesn’t work
–> If I click on “Reply” below the comment nothing happens
– Can’t upload any images
–> I always get an HTTP 500 but the image is added to the gallery
– flattr widget does not work
–> PHP error

What I did so far:
1) Backup of the DB
2) Backup of all files
3) Reinstalled 2.9.2
3.1) Deleted wp-admin and wp-includes
3.2) Deleted all files in root except wp-config.php
3.3) Downloaded a fresh wordpress 2.9.2 from www.ads-software.com
3.4) Unzipped the file
3.5) Copied the unzipped files to my server except the wp-content folder and the wp-config.php file.

–> Same problems. Any ideas are welcome!