I can run VBA code in ArcGIS10 now. The VBScript code came from Model Builder. I made models in ArcGIS 9.3, then I exported as VBScript. But in 10, the Model Builder can't export VBScript code any more. It only supports Python Script... :(
Do you have VBA license installed? In 10, you need to install license separately. Request support for the license.
I beleive the location of toolboxed is incorrect. I think this is new to version 10. The path to toolboxes on my machine is: "C:\Users\UserName\AppData\Roaming\ESRI\Desktop10.0\ArcToolbox\My Toolboxes"