Yes I'm having more issues.
I tried to upload all the files from client area and run upgrade - but it lists me paths to files in red, and tells me that if these were uploaded correctly then to fix permissions. I fixed permissions and still the same problems.
So I decided to run a fresh install, deleted everything and installed forum. But then database does not want to import/work correctly, there is one error saying that calendar table is already in the database. Then when I continue to forum, it's broken, user accounts are not imported etc, forums seem to be imported together with posts, but even ACP does not work as it should and I'm getting errors.
I decided to delete everything once more, upload the old backup and use it with old database.
Was there some major change to databases in versions 4.x.x? I don't understand what is going on, and why old database (version 4+ too) did not want to work on latest forum?