I've upgraded from v1.2.6 rc2 to v1.2.6 and got:

Quote:Warning: session_start() [function.session-start]: open(/tmp/sess_7575d97fd3cb9bdfb4db73f9c5a73485, O_RDWR) failed: Permission denied (13) in /.../photos/zp-core/admin-functions.php on line 10

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /.../photos/zp-core/admin-functions.php:10) in /.../photos/zp-core/admin-functions.php on line 10

Warning: Cannot modify header information - headers already sent by (output started at /.../photos/zp-core/admin-functions.php:10) in /.../photos/zp-core/functions.php on line 1803

Warning: Unknown: open(/tmp/sess_7575d97fd3cb9bdfb4db73f9c5a73485, O_RDWR) failed: Permission denied (13) in Unknown on line 0

Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct () in Unknown on line 0
Besides all diacritic signs in my gallery went away ...
Whats the problem ????

Few days ago I did the same from RC1 to RC2 - no problem.

Can anyone from development team help me ?

I recommend to do a fresh new upload. There probably something went wrong.

Permission denied errors are problems with your site. Perhaps some file security change.

I removed zp-core, zp-data, all root files and did fresh install. In the meantime I discover that you change db tables prefix (from zphoto to zp) so I got fresh gallery. I recover some contents from last backup and it seems it works ok. Fortunatly all my photos had been left in their albums.
I really didnt do nothing more than during previous upgrade (from RC1 to RC2).

We did not change any prefix--that is something you set. But of course, you may have used the default (zp_) rather than what you used the previous time.