MP3 thing: late LimeWire 3.9 betas and 4.0 introduced support for ID3v2.3 tags. The tags are kept in memory and everything is fine as long as the tags are not broken etc etc. Sorry, I cannot go into details here. Feel free to register and write me an PM. I'll forward this to the LW devs.

One thing though, how many MP3s did you share? Hundrets? Thousands?

You could experiment with the files a bit. Remove for example all files from the shared directory, share only MP3s and so on (important: you must restart LimeWire everytime).