Hi Pete,
First, I did search the Captain Sim F104 support pages but the problem was not indicated, only coming to light later as problem No. 290 on their list of more general problems affecting other products too. Also, Captain Sim produce some state-of-the-art add-ons, such as the C130 Hercules and one could expect their products work as advertised.
Sure, once the problem is identified it is easy to fix. The F104 now works just fine, as does FS2004 with the newer FSUIPC dll installed after the F104 but, as I said, for some of us this is just working in the dark.
Perhaps I should have titled the post " Older add-on causes FSUIPC conflict," but I am genuinely grateful for any information that leads to a better understanding of MFS.
Cheers