I have been using the latest svn version of TeXstudio happily until a while ago. Then, I happened to install the TeX Live 2012 pretest and removed the 2011 version. From that time on, TeXstudio has not been able to start any TeX commands liike xetex, pdflatex, etc. I removed the whole installed TeXstudio, recompiled it and installed it anew, but it still doesn't work.
(The command PATH is correct. I can use command line or TeXworks with the TeXlive 2012 pretest but not TeXstudio.)
(My old TeXlive 2011 was in /usr/local/texlive but the new 2012 is in /home/pan/texlive folder.)