Hi Bob.

No luck with that avenue of diagnosis, I'm testing on three different Win 11 24H2 hardware platforms and all three have the full suite of ACP apps installed, the working observatory PC, the 'old' observatory PC which I keep as a backup and a Win 11 (ARM) VM running on a Mac, where I write and test my VB and Java scripts for ACP before deployment to the live observatory PC.

I looked for the Common Controls 'COMCTL32.OCX' and 'MSCOMCTL.OCX' in the SYSWOW64 folder, which were both present on all three machines and are the latest versions according to web links that reference an old MS knowledge base article KB896559, (now obsolete), and ran the regsvr from a CMD prompt on those just to verify that Planner could find them if required, but the problem runtime error '438' still occurs when attempting to import a previously created plan.

A dead end I'm afraid, whatever is triggering the runtime error '438' it isn't the MS Common Controls, unless these are no longer fully compatible with Windows 11 24H2.

William.