ninathing

I’m having the same problem, does not work at all with custom permalink structure. Same setup as Matteo, same exact error even with all other plugins deactivated.

I was running WordPress 2.9.1 + the previous version of Simple Tags. It happened when I upgraded Simple Tags to the newest version. I never ran WP 2.3 or anything like that at all – I installed WordPress last December and I’ve kept it and all my plugins up to date ever since.

The problem was solved by removing the plugin and restoring my posts from a backup file. Haven’t had any issues since.

After updating this plugin (to 1.7.4.2, on WordPress 2.9.1), all of my tags and categories disappeared and all my posts showed up as untagged and uncategorized. I had to uninstall the plugin and restore a backup file to get everything to show up again, and had to manually tag and assign categories all over again. Luckily my blog is fairly new so I didn’t have that many posts to fix. Either way, I won’t be using this plugin again. It’s one thing when a plugin fails, it’s another when it screws up a whole web site.