The N button doesnt work.
It shows Cyanoboot screen and then load up cwm, pressing N button doesnt stop this.
And of my supprise also in cwm i couldnt mount sd card so i had to go into adb magic to mount media to mmcblk0p10 and then push cm9.zip and flash from there as i didnt have any rom on the internal.
After flashing cm9 with correct boot.img all back to normal.
Just for report.
After trying to flash Kindle fire kernel, my NT never reached cyanoboot bootloader, it showed N screen then bootloop.
So something needs fixing in Cyanoboot.
What i mean is, even with wrong kernel wouldn't be normal to pass cyanoboot loader and bootloop after trying to load from emmc.
Why kernel messes up bootloader? Weird!
1. Cyanoboot is not meant to work on the kindle fire, and the kindle file kernel should not be used with the nook tablet. The only devices cyanoboot works with is 1. Nook Color 2. Nook Tablet, and there has been development on 3. The lenovo A1.
2. The kernel must be added to the boot.img (sd) or boot partition (emmc) in a very specific way. If you did not do it properly, you will not see past the "N" if you are booting from emmc. This is described in the OP in some detail.
3. It would not be normal to get past the cyanoboot loader if the kernel was not properly added to the boot image. Again, see the OP for how it should work. It would not be expected to do anything with a kindle fire kernel.
4. It's extremely hard to make an evaluation, especially without knowing exactly what you did to "flash" this kernel. What makes you think a kfire kernel would work? If you're interested in using an experimental 3.x kernel, see the 3.x kernel thread.