Go trough the kernel recompilation again. Or did you install from binary sources? In that case you need to obtain the older kernel along with it's dependencies; I'm not sure what packages you have to get, but check out from your package management software. Since the difference seems to be minor (according to the kernel version number differency), you probably don't have to do any major changes.
Have you spared the older kernel, or tried if it works? It isn't wise to remove old working kernels, if you later need to boot them.
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