Code:
SystemTree.Nodes(0).Nodes("VIDEO").Nodes.Add(queryObj("Caption"))     <------ This Works
SystemTree.Nodes(0).Nodes("VIDEO").Nodes(CStr(queryObj("Caption"))).Tag = CStr(queryObj("Caption"))     <----- This Does Not
Error : Object reference not set to an instance of an object.

I have a similar piece of code which does not produce the error:

Code:
SystemTree.Nodes(0).Nodes("HardDrives").Nodes(CStr(queryObj("Model"))).Tag = queryObj("Index")
Both Caption and Index are of type string, so why does one work and not the other?

Computerman