I have two versions of my site - one live, the other a development site using DeskTopServer. I work on the development site - adding / editing posts etc. and making changes to the WP database, and playing around with templates, which are in a child theme. Periodically, I delete the live WP database and replace it with the development one. At the same time I ensure that the themes are in sync, adding any new templates and replacing amended ones.
The only difference between the two sites (that I'm aware of) is that some plugins are installed and activated on the development site that are not present on the live site. These plugins only do things 'back-end' - i.e. to do with admin stuff to make my life easier when working from the dashboard. Although they're enabled when I export the WP database to the live site, once it's there they're automatically deactivated because they don't exist. This therefore shouldn't (and as far as I know to date doen't) affect how the live site works.
I've just added a new custom taxonomy and a new template to display custom posts with that taxonomy. This works perfectly on the live site, but on the development site generates a 404 error. I've tried deactivating plugins on the development site that are not on the live so that the two should be completely identical, but that doesn't solve the problem.
I have one plugin - active on both sites - which does occasionally lead to weird things happening, but it has a 'clear cache' facility which once cleared has always also cleared any problems in the past. The plugin is such an integral part of the site that I can't deactivate it without breaking most of the templates etc. (It creates custom post types, custom fields, etc.) If I switch to the standard theme, the development site still leads to a 404 error, the live site still works.
The live page is here though as I can't also show the offline development page, the link probably doesn't help much!
This isn't a catastrophe, at least it's the right way round. I can, if I have to, live with a slight hiccup on the development site, but it's bugging the hell out of me to not be able to work out why it should happen.
Does anyone have any ideas?