I have had this problem on a new install of the UBB while testing. When I had done an update from one ver to the newer one it worked properly.
What I had to do is access the server VIA command line, yes it was telnet and it was a secure link for those of you afraid to use telnet for rumors of your connection being hijacked and taken, and had to use the command CHOWN on the folders for the gallery then CHMOD.
After doing this the gallery worked perfectly. I think there may be a glitch somewhere in the software that creates the folders and permissions when creating a gallery in 7.3
