In recently nightly builds of windbgx, I've noticed it has changed the initial default step behavior, or source mode. Typically while source code debugging, when you press F10, or 'p', it steps by one line of code, which is called source mode. Windbgx has recently been defaulting to stepping by instruction, which is called assembly mode. A line of code is often several instructions, so you end up pressing F10 a lot to step through a number of lines of code which is generally not what you want if you have source while debugging.
The source stepping options are controlled by the 'l' command. Here is the documentation, but basically you wan the 't' mode to step by lines of code instead of instructions. Without the 't', the debugger is in assembly mode instead of source mode.
The command to go to source mode is the following:
> l+t
