OK, it's the second time this happens, but this time I got a screenshot
ScreenshotI just open a project file, go to Project->Build options and voilĂ . It seems you have to be very quick to get the error, so as soon as you see the menu go for it

Something interesting is the error changes sometimes. I just tried again and it said something else, but was similar.
Could anyone else try to reproduce it?
Just in case: SVN 3194 + all plugins enabled (the problem could be here).
"el sistema no puede hallar el archivo especificado" = "the system cannot find the specified file"