From the Gentoo bug trac at the top of the page
http://bugs.gentoo.org/show_bug.cgi?id=301321 I've tried and I can't figure out how to apply the patch to Ubuntu. It looks like it's an issue with the installer. It's been done for the Gentoo installer, but it may be a bit before apt-get or aptitude have the patch. Might as well just wait.
In the mean time, for those affected, the instructions in post #42 in this thread are the ones to follow. I tried the RC3 and RC4 distributions of Ubuntu last night, then ended up back to post 42 after installing and reinstalling the kernel over and over without sucessfully dpkg -i'ing the headers. Either way.. LIRC is still broke in RC4, hopefully it will work in RC5 or Final.