Your DMux implementation is correct. Your Not appears to be functioning correctly from the screen shot. There is likely to be a problem with your And. Make sure that And.tst is still passing.
One thing to try is to create a subdirectory under projects/01 and copy only the DMux files into it. If the test passes in that subdirectory, the you know the problem is with one of the chips in the projects/01 directory.
If you can't find the problem, send me a .zip or .rar of your entire
projects/01 directory and I'll take a look at it.