It happens on BitTorrent network ? Are you using the latest beta or the final build ?
SlotSpeed = The speed assigned to a single client.
example: With an upload limit of 30 kb/s and "Slotspeed = 8 kb/s" there are ~3-4 upload slot, to give a speed of 8 kb/s to each client. In eMule the slotspeed is 3 kb/s, and its a really low value IMHO.
The benefits of an high slot speed is to complete the transfer of the chunk in less time, but you set a slotspeed to high you may have an upload a bit unstable due to the clients not able to get your bandwitch.
I don't think that your problem is caused from that setting.
TrickleSlots: There are some clients in upload in a "standby" status. Why ? If any client can't receive his bandwitch for any reason (usually depends from him, not from us) this badwitch will be moved to a client that was in standby.
It improves the upload stability, without trickle slots if the clients in upload cannot receive your bandwitch, you'll not reach your upload limit.
Drop Blocking Slots: It drops after some time those clients that can't receive your bandwitch. Do not use it if you use an high value of Slot Speed, (8 kb/s, is not an high value), because more clients will not be able to receive that bandwitch and it will cause failed upload sessions.
Sorry for the bad english, if you want more information (with a better english) search in some emule wikies, they're surely explained on them.