I was on kernel power 42 when I upgraded to 44, that's when I got the freezing issue. Then I flashed back to the stock kernel using the flasher program. That allowed me to boot the n900, where I was able to downgrade to the 43 version. From there I upgraded to 45 and so far no problems. Of course I also installed the updated fcam drivers from titan for the camera. Hope this helps!

On another note, I have noticed that the n900 cannot be rebooted with kernel power 45? By reboot i mean using the hidden reboot button. Is this a known issue?