I have experienced this problem on my home pc when changing between ubuntu and Fedora 14 on different hard drives and dread having to do the same on our server.
I don't know yet if it works on a remote server but in desperation on my pc I zipped the whole ubuntu Drupal7 site, everything, drupal7, themes, modules, everything, then zipped the database using mysqldump.
Zipping the drupal 7 site meant that I did not have to mess with module and theme versions, settings for those, etc.
On the other hard drive I set up a database with the same username and password and used mysqldump to install the drupal7 database, then unzipped the whole drupal7 file into /var/www/html/ on the fedora 14 disk.
I checked that settings.php contained the same database name and password as the database then opened firefox localhost/newdrupalsite and it worked with no errors or faults.
To experiment I am about to zip the whole Drupal 6.19 server site and the database then try the same process to install that on my home pc.
I have had no success with recommended methods which produce the same error messages that you get. We are not able to check nor change apache2.conf or httpd.conf on the server. Roger
Roger