Clive,
Not many, no. I tried to "fake out" OH by changing the attributes of the OHP and so on; however, I wasn't able to trigger the exception. Instead, I got nicely worded error messages, so I suspect that there's at least one QA Engineer at Borland who is as sneaky as I used to be. :-}
I'd guess one of two things:
1. There are problems with the Registry. You should be able to fix those by choosing File | Clean Registry from the OH main menu or by running the Registry fixup from the installation CD. (If memory serves, it's one of the options from the install program.)
2. This was a problem, but was quietly fixed in one of the service packs. Check out
and see if there's one available for your version of Delphi. (Note: Borland's site regrettably requires Javascript. *Sigh*)
Other than that, you might try to copy the OHP file from your install CD and then try again. (Don't forget to reset the Read Only attribute before trying to save your changes.) Granted, you'll lose the additional topics that were added by any third-party components, however, it might help you get past the initial problem.
Hope this helps...
-- Lance