The debugger from mma version 10.0 to 10.1.0 is broken for me. I have Windows 8.1 64-bit. When I step through a function using the debugger then the function is run several times. This problem didn't happen in previous mma versions. For example:

f[]:=Module[{},
x=1;
i++;
x=2;];

If I then run

i=0;
f[];
i

I get 1.

But if I turn on the debugger, and put a breakpoint at line x=1, and then continue after the debugger stops, my result is 2. And if I step through the function, my result is 5. This means the function f is run 5 times, just by me stepping through the function once using the debugger!

Does anyone else have this problem? Is it just Windows, or windows 64 bit versions of mma? Is there a known way to avoid this problem?