"Create content" descriptions not updating on /node/add page

I have a multisite Drupal 6 setup, one with Ubercart running. On the Ubercart site I've edited the descriptions of some content types in e.g. /admin/content/node-type/page. Although the updated descriptions show immediately on /admin/content/types they're not flowing through to the /node/add page. I've tried running cron, flushing all caches and clearing my browser cache but the descriptions stay the same on the latter page regardless. I've also edited the descriptions on another site on my multisite setup and there the updates flow through to /node/add straightaway. The two sites do have different themes (not sure if that would make any difference) but otherwise the only thing I can think is that with an Ubercart site you have a content type called "product" and when you want to create a different product content type you do so not with CCK but with the "product classes" bit i.e. /admin/store/products/classes - but this shouldn't affect content types that are nothing to do with Ubercart (e.g. a page), should they? ("Page" isn't showing up in the Ubercart product classes section.)