@Zei: You may have some bad cc. Split the large chunk of new cc into two halves. Take one half out, see whether the game loads. Try the same with the other half, taking the first half out. If one of the attempts loads, but the other one not, you at least have an indication on how to go further. Try to keep creations by one author in one of the halves together, in case it's a systematic issue.
Other than that, the game doesn't like having to process lots of files. You can use S3pe to bundle stuff into single packages, which speeds up loading immensely. Note that there is a maximum size for these files, and try to keep track of what you packed into which file. Other than that, you could use CCMagic to do that for you.
