faild to boot both default and fallback entries

[wthpr0]

I'm getting this error on ubuntu server 10.04

faild to boot both default and fallback entries

now i know kinda why it's doing this becuse i'm trying to change the kernal it's running on. But now i can't find away to get back to original kernal :(

Here is the output of my boot folder:

root@bt:~# ls /mnt/hdb1/boot/
abi-2.6.32-21-server config-2.6.33.7-rt29.backup initrd.img-2.6.32-24-server System.map-2.6.32-24-server vmlinuz-2.6.32-21-server
abi-2.6.32-24-server grub initrd.img-2.6.33.7-rt29.backup System.map-2.6.33.7-rt29.backup vmlinuz-2.6.32-24-server
config-2.6.26-2-amd64 initrd.img-2.6.26-2-amd64 memtest86+.bin vmcoreinfo-2.6.32-21-server
config-2.6.32-21-server initrd.img-2.6.28.1 System.map-2.6.26-2-amd64 vmcoreinfo-2.6.32-24-server
config-2.6.32-24-server initrd.img-2.6.32-21-server System.map-2.6.32-21-server vmlinuz-2.6.26-2-amd64

btw: have it booted in BT4 right now since i can't boot ubuntu-server