Speaking of trying other player's firmware: If anyone wants to try an "alien" firmware, I suggest to try the player application first, without actually flashing. It's relatively easy.
* Download the firmware you want to try
* unpack/extract install.img
* install.img is a tar file, so rename to intall.img.tar
* unpack/extract intall.img.tar using 7zip, filzip, total commander or any tool that supports tar archives
* once unpacked, you'll have some some files and a folder called "package2". enter this folder and look for a file called "yaffs2_1.img".
* This is another archive, this time in yaffs2 format. (It contains the roof filesystem of the device).
* Download unyaffs.exe from here (or other place, use google): unyaffs2.exe
* Copy yaffs2_1.img and unyaffs.exe side by side to a new, empty folder, and extract the archive using the command "unyaffs.exe yaffs2_1.img".
* you'll get a number of folders, like bin, dev, etc, usr, ....
* navigate to "usr", then "local", then "bin". you should see 2-3 folders, and a number of files here, amongst them a file called "DvdPlayer"
* copy everything from this folder - including subfolders - to an empty usb stick's root folder.
* plug the usb stick into the player
* open telnet, log in
* navigate to /usr/local/etc, and make a copy of the dvd folder, including subfolders. (cp -r dvdplayer dvdplayer_backup)
* stop the running player application: /usr/bin/stopall
* start the new application from the stick: /tmp/usbmounts/sda1/DvdPlayer (assuming that you copied it into the root of the stick).
* enjoy (if it's working)
* if it doesnt work, you may try to delete the user setting files in /usr/local/etc/dvdplayer and try again
When you finished testing, delete /usr/local/etc/dvdplayer (and all subdirs) and rename/copy back the original files: "cp dvdplayer_backup dvdplayer"