I can recommend media player classic, too. Mpc has a far fewer problems, but the problem might not be with the player in this case.
If opening files into the mediaplayer stalls, the issue might be with some codec. Time the delay. If it's exactly 30 seconds or some other suspiciously round number, we have a winner. If you're feeling bold, you can get filemon and regmon from
http://www.sysinternals.com and try to determine if there's some file/registry access from the app during the stalling. If there is, it will probably help you determine the codec responsible for lagging which can then be unregistered.
Obviously, debugging problems over the web is quite quite troublesome, issues like these are usually approached with a proper debugger, too, not just lightweight "maybe I'm lucky" debuggers. However, if the issues happen with every video player application you use, it's probably a codec issue.