To get IMVU v471.0 to work with Sandboxie, follow these steps:
1) Open Sandboxie Control,
2) Click the sandbox menu option
3) Then click "Create New Sandbox" and name it.
4) After that, right click your new sandbox and click "Run Sandboxed", then "Any Program".
5) Navigate to the IMVUClient folder and choose "IMVUClient.exe".
DONE!
If you don't do this and you try using the default Sandbox, imvu will either give you memory errors or bug reporting errors and just close.