Today one of our fantastic users informed us of an issue they were having with the new release of MCG. The problem is that MCG 3.0 was written to import documents based on the callgrind specification and we were unaware that Xdebug provides functionality to concatenate profiles into one file, but it does so in a way that is against the standard.
We've now fixed the issue and are awaiting App Store approval, but in the meantime there are a couple of options available to work around the issue. The first is to disable profile appending in your xdebug.ini.
Or you can remove some output lines from the resulting file.
grep -v "^====" cachegrind.out.appended > cachegrind.out.new
Our preferred option is to change your Xdebug settings because MCG currently doesn't support having multiple profiles in one file; unless you actually want the sum of the costs over multiple files. We are however working on a solution to allow opening selected profiles from an appended file.