Are you by chance using a Vista beta?  Noone has reported the problem you are with 3D models, so it makes me suspicious of a system-level difference.

I have also not heard of an issue related to file size and sounds, and will test that. 

Just yesterday I added a new downloads folder for Programming Resources, and started adding sound files into it: http://phrogram.com/files/folders/soundfiles/default.aspx

Many more to go.  We'll use the same area to store 2D and 3D images as well.

I also just added a User Uploads area for files - if you have any non-copyrighted ones you'd like to upload, please feel free.