Visual Studio 2010 debugger steps over methods and doesn't stop at breakpoints

My Visual Studio 2010 debugger sometimes has a very strange behaviour...

Sometimes it doesn't stop at breakpoints, but when it stops, and I want to step into a method, the debugger just steps over it. Also the breakpoints in those over-stepped methods are ignored.

When this strange behaviour occurs, it also does not break on exceptions but simply ignores them.

I've tried to rebuild my project, reset the Visual Studio settings and disabled debugger settings like "Break only in my code", but nothing has worked.

How do I solve this problem?