Hi Burl,
We've been having troubles with the repository for several days, I've reported it to the codeplex team and hope to hear back from them soon.
I can say that I managed to clone it just now by using https://hg99.codeplex.com/mojoportal
but I had to branch down the options for cloning and choose "Clone to revision" and put 0 for the revision. Then it succeeded in the clone and I was able to open TortoiseHG Workbench and pull changes, then finally right click the top folder and do HG Update to update the working copy to the latest revision of the default branch.
Hopefully that will work for you anf hopefully they will resolve the problems soon.
Best,
Joe