Help with Folder permission problem with Oracle DB 7 and Solaris 7

I was wondering if anyone else has come across this issue with Solaris 7 and Oracle Database 7, I set the permissions of the folder as such chown -R oracle:dba /opt/oracle but when trying to install the database I keep getting permission denied even no I set it and I checked and it all had read/write/execute but soon as I goto installer and get to ocommon section it resets the permissions back so that the gorup dba no longer has write permission, anyone got any ideas ? Thanks, yours Simon