I also have this problem, but restarting doens't help. I even reinstalled Lazarus (0.9.16), and still the same. I can't even run the program with F8, and if there is a run-time error it never highlights the last line in the project source - it either doesn't highlight anything, or highlights a line in an lcl source file. What's funny, breakpoints work well in the lcl source files, e.g. I can set a breakpoint in control.inc, and it will work for my project. Maybe I have something wrong with compiler settings. Which settings could cause this behaviour?