AFAIK Code::Blocks only uses its "internal" log which is displayed in a wxTextCtrl and accessed through a tab, so if you cannot get Code::Blocks to display its interface you won't get access to the log. In other words, no log file is created.
Have you checked if the codeblocks.rpt file is being created?
You could also try running Code::Blocks through GDB, or just trying plugin by plugin.