What options did you select when you installed Visual Studio? I know the VirtualTreeGrid is used with the class diagrams for the VB and C# languages (you should have at least one of these installed). The treegrid is used as part of several other designers as well, but most of those are in the higher-end SKUs.
I ran the Google hits and found some virus-related hits on Microsoft.VisualStudio.VirtualTreeGrid.resources.dll, but none on Microsoft.VisualStudio.VirtualTreeGrid.dll. I was unable to find an explanation of the security threat, just that the dll could be used to gain control of a machine. Visual Studio does not install a resources dll for this control. AFAIK the control itself is fine. I know for sure that the control is straight .NET (nothing unsafe) with some external GDI Windows API calls. So, if you can get it to install with sufficient VS installation options then you should be fine.