Seems like all the nuget packages are missing from the Syncfusion Nuget repo...
http://nuget.syncfusion.com/nuget_aspnetmvc/nuget/getsyncfusionpackages/aspnetmvc
http://nuget.syncfusion.com/javascript
http://nuget.syncfusion.com/aspnet
to name a few. Looks like they are all affected tho.
This preventing VSTS from building solutions that reference nuget packages.