Because I’m still getting questions on compiling psptoolchain on Ubuntu 8.10 (Intrepid Ibex), I should note that the latest version of psptoolchain from the trunk of the SVN repository fixes the compile-time ‘buffer overflow’ error, by forcing the compiler to use GCC 4.2.
Make sure you have all the prerequisites before compiling, including GCC 4.2 — the default installation of GCC on Ubuntu uses 4.3. Both 4.2 and 4.3 can be installed simultaneously. When installing, use the psptoolchain-sudo script.
I should also mention that you’ll get far better help by asking the developers of psptoolchain, by posting in the ps2dev forums.
I'm a programmer with too much interest in too many programming languages, and not enough time.