Through Windows Skydrive I am able to open and view the files in LiveMesh. That is I can open and view all of the files except .xls, and .xlsx. The browse doesn't even show excel.
Just FWIW instead of letting Skydrive save the xlsx file to the default location, I did a save as and saved it to my desktop. Yup it was unassociated. I added .xlsx to the file name and it opened w/o any problem. So I am now thinking that either LiveMesh or Skydrive is striping away the association?