"Could not find MathLink executable." Error message

I keep getting a “Could not find MathLink executable.” error message from Mathematica 8 on MacOS. I looked around and this seemed to be a possible fix: http://superuser.com/questions/378767/linkopenlinke-could-not-find-mathlink-executable however, it did not seem to work. I am attempting to call Mathematica from within a Mono program. I added the appropriate path as suggested here: http://mathematica.stackexchange.com/questions/20765/running-net-link-on-mono-on-macos-or-any-unix-or-linux-distro but I’m still getting the error. Any suggestions?

The update of Mathematica and the PC are necessary. After that, the work will be pleasant, because you will work effectively.

I now have Mathematica 10 for mac. I’m still getting the same error when attempting to run the examples:

LinkOpen::linke: Could not find MathLink executable. >>
InstallNET::fail: A link to the .NET runtime could not be established. >>
LinkOpen::linke: Could not find MathLink executable. >>
… and so on.