freemangordon, let me help you, here is simple answer to kernel-related questions (people, please read my whole post, not only first paragraph and don't ask questions which are answered in following paragraphs):

To whoever asks about kernel: after update to css-thumb, current version of kernel power 50 will not work, will be uninstalled and can never be installed again without damaging system on n900.

If you install cssu-thumb now when it is in highly experimental and unstable state, the ONLY kernel which will work is kernel-cssu. It will break all packages depending on kernel power.

If you cannot understand this, but have at least a bit of computer knowledge, I can try to explane it to you this way: imagine this update is like updating Windows 98 to Windows 7 64bit - there is a lot of integral operating system parts compiled for these newer kernel and this new parts of software require this new kernel to run. If you flash older kernel (kernel power 50) and reboot, it would be like trying to run recent software (e.g. MS Office 2010) on old Windows 98 - it will crash really badly.

If you want to install cssu thumb safely, wait for it to become stable, now IT IS NOT SAFE, it can crash at any time without any reason visible to end-user (so if you're not a programmer, you probably shouldn't use that).

If you want to install cssu thumb without reboot loop, you have to forget about kernel power existance, just stick with the kernel installed with this update.

Did I make it at least a bit clearer to any of you with questions?