I have. a simple question. After I updated my kernel, I couldn't boot (stuck on purple screen) unless I chose the old kernel. So how do I delete the new kernel with synaptic. And how do I do this safely? I'm in Quantal Quetzel. My kernel is 3.5.0-40. The working kernel is 3.5.0-39. Also, how do I stop kernel updates from appearing in the update manager? Thanks.
To safely remove the unwanted kernel, open a terminal session and run the command:
Find the kernel package name
On amd64/x86_64 it is linux-image-3.5.0-40-generic.
Remove (purge - remove all configuration files as well)
I will suggest you always keep at least one older kernel available, just in case you need to boot into it for reasons you may never expect right now.