In a word, d’oh!
Spent a while trying to work out why I could install the Google Analyticator plugin but then when I tried to customise it from its option page, or go to any other link on my site from it I got a 403 Forbidden error. Looking at the Apache logs didn’t give much help, it was just whinging about
client denied by server configuration and I was completely stumped, so I thought it must be some weird bug and installed Rich’s Analytics plugin, but that had the same problem!
But the fact that two plugins with similar names had the problem, whereas others were finally caused the penny to drop – I had installed a whole bunch of .htaccess to prevent comment spammers from getting too many links in and if they match they return with a 403 error. Turns out that one of them was broken and matching on the “anal” in Analytics!
Sigh.. at least it works now!