if you overly use friends slots in some clients, or you powershare an incomplete file, you get 'penalised' to a 1:3/1:4 ratio. Meaning you aren't uploading enough.
You will see a small r next to your download in the bottom right of the emule interface if you are getting near to the hard coded ratio, and a large R if you've reached the 'leech limit'.
Get rid of all the friends slots and/or powershared imcompletes and it should go away. If it remains, the reason is that your downloading way more than your uploading.... normally means you've got your upload capped artificially low.
~20-28kb/s up for 256, and ~10-12kb/s up for 128 are the normal settings that won't effect performance
