hi Zoro,
Welcome to the site. The reason files = to or less then 32b are working is because WinMX is designed to auto upload those. Meaning you dont have to wait in a 'Que' for them. This is because most OpenNap files (.wsx files) are below that and this helps to get those spread around.
It might help you to know that if your files say 'Remotely Queued' and are purple your in line for the file. And you just have to wait your turn, video files can take some time to get.
If they are saying 'Timed Out' or any other Red Message then go to the Settings > Search > on the right look for 'Default Download Parameters' Under this you will see Auto Enter Que (aeq - remember previous settings) Click this and choose at least 50.
You may also want to change your already started files settings. Highlight the file name in the transfers screen or right click and choose the Auto Enter Que - 50. This should help you get in queus that are typically longer for video files.