I tried to add an existing database (DDF and MKD exists, security is on the DB, RI is used) in PCC by performing following steps:

1. select new database
2. enter the name of the database
3. enter the path to the database
4. OK
5. I get an message that I have insufficient rights

If I uncheck the create DDF and integrity enforce flag, it works, and later on I can set the integrity enforce flag in the properties of the database.

I am sure in older versions I could do it by performing steps 1-4. Now I am using 10.10.

Do I some mistakes or is it a problem of PSQL10.10 or are there other reasons for such behavior?

Perhaps you are running in a remote desktop or terminal server session?  Or, maybe we think you are?  See if you have the WTS key, and if so, change it to 0.  Details are here:

No, I have this problem on local VMWare installation with P10.10 WG and on Win2003 Server with P10.10 accessed by Remotedesktop, but Registry setting are correct.

On both systems I am able to create a new Database in a temporary folder and to change the directories in the properties of this new database so that original DB files are accessed. But in this case, if I open the database I get a message "Invalid user authorization spezification".