>>You changed the interface. that's why. Early binding breaks when an interface changes.
>
>Ed,
>
>You are right and you are wrong:
>I did not change the interface from my point of view, just the implementation.
>I did change the interface from VB's point of view: I had the 'no compatibility' radio button checked in the project properties.
>I changed this to project compatibility and now everything works as it did before.
>

When I say 'interface', I don't mean the UI implementation, I mean the programmatic references to it - CLSID, ProgID, properties, methods, and their parameters. If you change any interface element, the CLSID changes, so you don't connect to it the same way. If the CLSID doesn't change and some other aspect does change, and you've used early binding, which resolves method and properyty interfaces at compile time and builds a reference table, rather than politely asking through the IDispatch how to resolve things (slower, but results in greater compatibility and portability), things break if the new control's not quite exactly identical to how it was at compilation.