My site has the search engine friendly URLs checked under global configuration.
When I add the detail article to an event I'm getting a 500 error for article 297 for example - see the link below:
Hello. There is a parameter in each event where you can enter a specific Itemid to use for the Details link... right under the article selection. This is often needed with using SEF. Easy fix though... enter the Itemid. See this post for more details...