After a few wrong turns...
Downloaded a fresh copy using the package manager. Deleted the embedded zip.
I didn't regasm the new download.
Sample worked okay.
Added my LibXL Licence keys.
Sample again worked okay even though its still Mike's LibXL and LibXL.net dlls in the programs folder.
AND specifying a decent key gets rid of the warnings on line one of the output samples, even though they key doesn't match.
Copied my LibXL-supplied LibXL.dll into programs. Comm error 4399
Copied my LibXL-supplied LibXL.net.dll into programs. Runtime error 'runtime newer than currently loaded runtime'
[code]
C:\Users\DAve.KIRKFREEPORT\Desktop\StarZen.LibXL\P rograms\LibXLSample.exe
COM object method invocation error. Could not load file or assembly 'libxl.net, Version=3.6.3.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.

Error: 4399

GET_COMCREATEBOOK (10381) - oLibXL (225) - at address 70893
GET_CREATEBOOK (10423) - oLibXL (225) - at address 71310
MSG_ONCLICK (4659) - oButton3 (227) - at address 71371
MSG_COMMAND (648) - oButton3 (227) - in native code
[start] - at address 71546
[code]

So, does szLibXL.dll need to be rebuilt for later versions of LibXL?