Found a very interesting bug in Windows Media Player (WMP).  An embedded player will fail to play if the URL of the page it is embedded into is too long.

This is fun because you can see this on any website. I have only tried this in Firefox and Internet Explorer 7 on Windows, but compare these URLs:

Page with short URL

Same page with long URL parameters added

The WMP APIs are pretty embarrassing, but for me, this one takes the cake.