If you had waited until recently to upgrade from 1.4.19 to 1.4.26 then your site could have been compromised. Exploits were being used/tried against the older cpg versions long ago.
Why don't you just open and compare the tables? See for yourself what has changed.
Additionally you should read and follow the procedure outlined here: Yikes, I've been hacked
As far as I know 1.4.19 and later versions do not have any db differences that would not be handled by update.php. If you are now actually running 1.4.19 then your site is again at risk for being compromised.
Hi,
This is an update what actually is happening.
1) Running 1.4.19 in some way (hacked?) the usergroups dissapeard. (Gone in the database but users are there)
2) Reading a post about dissaperaing users and groups I upgraded to 1.4.26
3) Groups still gone and now I got the "Selected user does not exist !" Error in several places in the gallery.
4) Adding the groups from a backup into the database, the users and groups show up fine in the gallery, but still the same error message (And the debug output as mentioned above)
5) In just a test I switched back to the 1.4.19 catalog (still same database) and log in.
6) The log in works fine, no error message. But!
The usergroups was wiped out from the database!7) Repeated to add the groups back from a backup. And viola it works fine in 1.4.19 mode...
So it seams that is two diffrent problems here.
A) Regarding 1.4.19 and it wipes out the usergroups database (What I actually thinks happened in the first place, since no evidence of hacking is found (yeah they could be nice and clear all logs, but no other bogus traffic or rootkit is installed either soo...)
B) Regarding 1.4.26 that gives me the error output, that something is changed in the code between this two versions, "cpg_db_query"?)