We have just released Magento Version 1.0.19870.2. This version includes a few bug fixes, detailed in the release notes.
Instructions for Upgrading Magento with a full package, via SVN, via the MagentoConnect Manager and using SSH shell access are available in this wiki post.
After upgrading Magento to this version you will have to refresh the layered navigation indices.
Please go to ‘System’ -> ‘Cache Management’, check the ‘Refresh Layered Navigation Indices’ box and click on the ‘Save’ button. This operation might take some time depending on the number of products and stores in your database.