Delphi: why breakpoints from time to time are not usable (green highlighted line on IDE)?

Question

From time to time I lose breakpoint functionality in Delphi.

I thought this to be a Delphi 2009 issue but now I have also it in Delphi XE.

In Delphi 2009 by

Answer 1

I found a better way.

From the Project Manager tree, right click on the project and choose "Clean" from the popupmenu.

The breakpoints reappear magically and it is a very fast method.