ORA-00000 is not about Unique constraint violating. This is actually not an error message, it's more like an "informative message", which says "Everything is OK".

From Manuals:

ORA-00000 normal, successful completion
Cause: An operation has completed normally, having met no exceptions.
Action: No action required.

I think you should check your VB code/settings (I know nothing about VB), somehing must be wrong there.