apt-get does not give you matching kernel sources, you needs to compile the kernel sources from dvd which matches your PR release.

PS. If you want to boot into apt-get kernel, then you also need to copy/install all the matching kernel modules to /lib/modules/current before booting to your kernel. Flashing zImage only is only possible when you compile kernel that matches your PR release with patch applied. In all other combinations (like apt-get version, vanilla without patch or changed kernel config) you need also install all the kernel modules (to /lib/modules/current/) before you boot to your new kernel.