[support] multiple issues after downgrading...to export/migrate manualy?

[zeljko blace]

Dear friends,
In recent attempts to upgrade a fairly elaborate and content packed Drupal site
(hosted at 101sitehosting and managed "mostly" through web interface
of installatron)
we failed to successfully upgrade from 5.x to 6.0 version of Drupal.
As script gives option to downgrade the installation we tries to do so
and site is again operational but quite a few content-type related
issues appeared
(articles, forums, book pages got mixed up).

What would be the good way to export existing content+users and
import it into new 6.0 setup
or maybe even to import it first to new 5.7 setup and then re-try the upgrade?

Thanks for any advice given!