I've been getting this error message in the debugger console of Xcode, while trying to debug some iPhone apps. At the same time it appears that GDB is freezing, after hitting a breakpoint and trying to step through the code, with the app being debugged eating up the available CPU juice.
Even if my app were very buggy, this still wouldn't be a reason to hang GDB, so I was starting to suspect that it may be a GDB issue. I discovered that if I moved my breakpoints the problem would disappear.
For example in the screenshot below, if I set the breakpoint anywhere on the lines 30-34 the problem appears, if I set it to line 36 the problem goes away.
While I don't know the root cause of this, a workaround is to move your breakpoint past the trouble zone.