POL needs to have the manual installation of games updated so that you can change cd's while installing. The only way I have found around this is to copy all the cd's contents into a folder and install the game from that folder. Every time I try I get a cannot unmount error and thus cannot change the disc to continue installing the game/software.
My gut feeling is that installations script(s) have the (possibly needed?) habit of making chdir to the mounted CD, which prevents the CD from being unmounted. You can try one of the following in a terminal window and see if it works for you:
umount -f /media/cdrom
Change "/media/cdrom" to whereever your CD is mounted. I ran the "eject" command when the DVD-reader eject button did not work at one time, and the disc was ejected, so perhaps it will work in your case if you are lucky.