Was able to boot 2.6.28-11 using "initrd.img-2.6.27-13-generic"
chanakya:~$ uname -a Linux chanakya 2.6.28-11-generic #40-Ubuntu SMP Fri Apr 3 17:39:41 UTC 2009 x86_64 GNU/Linux
chanakya:~$ ls -al /boot/initrd.img-2.6.2* -rw-r--r-- 1 root root 9320843 2009-01-30 14:40 /boot/initrd.img-2.6.27-11-generic -rw-r--r-- 1 root root 6399859 2009-01-30 14:40 /boot/initrd.img-2.6.27-11-server -rw-r--r-- 1 root root 9320778 2009-02-22 21:28 /boot/initrd.img-2.6.27-12-generic -rw-r--r-- 1 root root 6400297 2009-02-22 21:27 /boot/initrd.img-2.6.27-12-server -rw-r--r-- 1 root root 9320581 2009-03-05 11:37 /boot/initrd.img-2.6.27-13-generic -rw-r--r-- 1 root root 6558642 2009-04-07 16:10 /boot/initrd.img-2.6.27-13-server -rw-r--r-- 1 root root 8635079 2009-04-07 20:21 /boot/initrd.img-2.6.28-11-generic
Note the substantial size difference between the non-working "initrd.img-2.6.28-11-generic" (8.7M) and the working "initrd.img-2.6.27-13-generic" at 9.4M
Was able to boot 2.6.28-11 using "initrd. img-2.6. 27-13-generic"
chanakya:~$ uname -a
Linux chanakya 2.6.28-11-generic #40-Ubuntu SMP Fri Apr 3 17:39:41 UTC 2009 x86_64 GNU/Linux
chanakya:~$ ls -al /boot/initrd. img-2.6. 2* img-2.6. 27-11-generic img-2.6. 27-11-server img-2.6. 27-12-generic img-2.6. 27-12-server img-2.6. 27-13-generic img-2.6. 27-13-server img-2.6. 28-11-generic
-rw-r--r-- 1 root root 9320843 2009-01-30 14:40 /boot/initrd.
-rw-r--r-- 1 root root 6399859 2009-01-30 14:40 /boot/initrd.
-rw-r--r-- 1 root root 9320778 2009-02-22 21:28 /boot/initrd.
-rw-r--r-- 1 root root 6400297 2009-02-22 21:27 /boot/initrd.
-rw-r--r-- 1 root root 9320581 2009-03-05 11:37 /boot/initrd.
-rw-r--r-- 1 root root 6558642 2009-04-07 16:10 /boot/initrd.
-rw-r--r-- 1 root root 8635079 2009-04-07 20:21 /boot/initrd.
Note the substantial size difference between the non-working "initrd. img-2.6. 28-11-generic" (8.7M) and the working "initrd. img-2.6. 27-13-generic" at 9.4M