It looks like you do not have sufficient rights to load this assembly. You need to install the chart control using the MSChart.exe on that box. I'm not sure if it is possible in your hosted environment.
Is the type System.Web.UI.DataVisualization.Charting.Chart picked up from the GAC? It sometimes fails to load some assemblies from the GAC sometimes. Please add the corresponding dll in your bin directory directly and try running your app and see if that works out for you.
The problem might be due to the fact that you are referencing the type in your view and not in your controller, in that case you probably need to define the assembly info as a web.config setting or as a page directive.
<assemblies>
<add assembly="System.Web.UI.DataVisualization.Charting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=<YourPublicKeyToken>(31bf3856ad364e35)"/>
</assemblies>
REF:
Chart Error
Could not load file or assembly ‘System.Web.DataVisualization, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35′ or one of its dependencies
System.Web.UI.DataVisualization.Charting missing error in .net 4.0?