A couple of thoughts here since there isn’t much online and this project is on hiatus apparently with likely no support for Mono compatibility coming anytime soon.
1) Not sure what version or build you have of Gallio, but you may try the Gallio bundle nuget from here and see if you get different results with this version: https://www.nuget.org/packages/GallioBundle/3.4.14. See this post: https://stackoverflow.com/a/21185517/9798633
2) Make sure your tests are compiled with the same version of MbUnit as was distributed with Gallio, as discussed here: https://stackoverflow.com/a/2242849/9798633
3) If you try running in VS in a VM, doublecheck to make sure you have a Class Library project with references to both Gallio.dll and MbUnit.dll as mentioned here in “ASP.NET MVC 4 in Action”:
ftp://soporte.uson.mx/PUBLICO/02_ING.SISTEMAS.DE.INFORMACION/PVI/ASP.NET%20MVC%204%20in%20Action.pdf