Working with multibib, Bibtex started failing me after a recent reinstallation of texlive on xubuntu. On
bibtex <project-path>/src.aux
I got:

 bibtex: Not writing to &amp;amp;lt;project-path&amp;amp;gt;/src.blg (openout_any = p).

I couldn't open file name `&amp;amp;lt;project-path&amp;amp;gt;/src.blg'

To get rid of the error, open texmf.cnf, which resides in /usr/share/texlive/texmf/web2c through
sudo gedit /usr/share/texlive/texmf/web2c/texmf.cnf
Then find the entry

openout_any = p

p is the paranoid setting. I changed it to r and it now works again (chapeau to dmj).

[update 31 Jan 2013] If sudo is not an option and thus texmf.cnf can’t be changed, see Sini’s helpful comment below. [/update]

 

If you want to learn about multiple bibliographies using multibib, there is a very good tutorial by peisistratos. Unfortunately it is in German, but I’m sure there are English ones out there, too.