I recently added a large volume of products to Magento, however when I looked through the product listing, it was really strange.
All products were displayed correctly however the sort order was all wrong. Instead of being ordered or sorted by price as default, the products were all over the place.
After a bit of searching I eventually found the problem is in the Magento cache system and specifically in the Layered Navigation indexes.
Logging in as admin and using the “System->Cache Management->Layered Navigation Indices->Refresh now” option resolved the issue.
However this process took a long time to complete on my server, so some patience may be required.