I just set up MediaWiki for a test run on my laptop. Windows 7, PHP 5.4, SQL Server 2012 SP2, IIS 7, MediaWiki 1.23.6. The installation went smoothly once I got everything in order and I can create and edit pages.
On the Main page, I edited in a link to a Projects page.
The Projects link was red, as it should be, and I clicked it, made the page, and saved it. However, when I go back to the Main page, the Projects link is still red and the tooltip says "this page doesn't exist". Clicking on the link will take me to the page I created successfully.
How can I fix existing pages showing up as red links when they should show up as blue/purple?