are you using cssu stable or testing?
i have no issues with stable....
i do think you need to flash your n900 back to factory..
also from my experience its better to drag and drop your files from the n900 to your desktop and then back to the n900 rather than doing a backup restore....
if youre wondering why...from experience sometimes after a restore you can actually "replace" the bug from the restore....
a fresh start usually gets rid of any probs...