Thanks for your suggestions. Here’s what I’ve found out…
I’m running 1.1.6. I’ve tried upgrading to 1.1.8 through Magento Connect, but get stuck on packages requiring Lib_Js_Calendar to be newer than 1.0.18800, which is the only version Magento Connect seems to be able to find.
So I downloaded 1.1.8 and installed the new version in a different directory. I use Samba to connect to the in house dev server, so played around with the permissions a bit until I got things working well. Ended up with owner of apache:[my group name] for everything, with all folders & files set to 775 except the following which were set to 777: /app/code, /app/etc, /downloader, /.htaccess, /media, /var. This works perfectly - I was able to install the extensions and they were added to the Payment Methods screen.
Then I changed the permissions etc on the original 1.1.6 version to match those on the new version. But when I installed the extensions they were not added to the Payment Methods screen.
I tried the method suggested by mark092772 on the original version, but this made no difference.
So now I’m looking at transferring my work from the original 1.1.6 version to the new 1.1.8 version. I have done a lot of templating work already, but this should transfer fairly painlessly.
I’m still totally stumped on why my original 1.1.6 version wouldn’t behave or even update to 1.1.8. Any suggestions?
Thanks for your help!