From what I can tell, the main difference between Poseidon 4.4 and 4.5 is the included hardware drivers, and that 4.5 includes a newer version of Trident.
As for your DVD drive problems, one thing to have in mind is that unless Poseidon is started by using PsdStackloader in the Startup-Sequence, it will use the default settings, where the default for CD-ROM filesystem is AmiCDFS. This might be the reason why Poseidon seems to reset the settings after a reboot.
Anyway, the easiest solution for you is to simply start using AmiCDFS as filesystem. It isn't the best one around, but it's free, works very well with Poseidon, and it's also a LOT better than CDFileSystem. You can get it from here:
http://aminet.net/package/disk/cdrom/amicdfs240PS! I don't have a Deneb myself, but I assume that if Poseidon is started directly from the software included on the Deneb, it is not done by using PsdStackloader.
