..so close and so far away
You have done , what ever posible from your side . You cannot help , if the geode driver itself is buggy. It is already mentioned in bug-tracker site.
Now since you are mostly successful in rotating the screen, you must be knowing exact squence of commands. Now you can fine tune your system with different available options / work arounds on the net with due care to backup / rename all successful files first ! And try rotating sequence after every option.
For example :
1) Disable DRI or set AGP speed to 4x in BIOS settings , if posible in your BIOS.
2) Add :
Option "AGPFastWrite" "false"
.. , somewhere in .conf file - may be in card section.
By the way , most linux systems have a powerful command to show all the hardware details like cpu , monitor , graphic card etc :
inxi -b