I've update to linux-image-3.2.0-30-generic-pae 3.2.0-30.48 and now Ubuntu don't open smoothly and take time to boot but it's not that weird because I had this problem when I was using 11.10 all the time but some how when I upgrade to 12.10 it fixed, so now after I got like 3 new kernel images update the problem got to back again, what I'm asking here is how to bring back the old linux-image to system and you must know I have remove all the old kernels with Ubuntu Tweak janitor option so now only one I got is linux-image-3.2.0-30-generic-pae 3.2.0-30.48.
Just install the Linux images again
You should now have option for booting the previous Linux image. Boot to that image and remove the updated one.
If you really want to get a list of all Linux images, You can check the repository pool by going here
A screenshot is added below: