TeX Live error on Ubuntu 10.04: pdflatex.fmt doesn't match pdftex.pool

[I asked, then search the net. I've made my answer community wiki so as not to look like I'm rep-hunting.]

There was a bug filed against ubuntu 10.04 beta. I'm somewhat surprised it's not been fixed as it makes latex rather useless.

One commentator on the bug thread said that deleting /home/.texmf-var worked for them. Worked for me, too.

As mentioned in the other answers, the problem is caused by some local files not being updated upon an texlive upgrade. In my case fmtutil --all fixed the problem. (Neither sudo nor the fmtutil-sys version, those files seem to be upgraded by the package, just the stuff in the user dir isnt.)

I was having the exact same problem when I upgraded from 11.10 to 12.04 and then to 12.10 (even thought I'm a year behind). I could not compile latex, similar to the first post. This is what I was getting:

$ latex file_name.tex 
This is pdfTeX, Version 3.1415926-2.4-1.40.13 (TeX Live 2012/Debian)
restricted \write18 enabled.
---! /home/myUname/.texmf-var/web2c/pdftex/latex.fmt doesn't match pdftex.pool
(Fatal format file error; I'm stymied)

I used the solution stated above. Instead of deleting, I just renamed it. ie.

$ mv .texmf-var/ .texmf-var-BackUp

In my case, the .texmf-var folder was in the /home/myUname folder and not in /home folder. Now it compiles like it used to. Just wanted to add this in case others were looking for the same solution.