I recently released a level (you can see it in my sig), and previously I could run it just fine, but suddenly whenever I try to run it, or another compiled version of it, portal 2 freezes at slightly over half the loading dots filled. Apparently, however, this doesn't happen for everyone. Does anyone have any idea how to fix this?

Try reducing the length of the name of the map, it might work then.

Could also be that something has corrupted in your map since last time, a fix some people use is to select everything in the map (map -> map properties) and then copying it to a new map and renaming it.

Shortening the name fixed it.
Thank you,
Sound Logic