Actually something else has changed too. LimeWire has started to cluster its nodes to shield you from traffic. You are receiving less upload requests from non-limewire hosts. Normally I would assume that limewire users and other gnutella users have the same download behaviour, but maybe this is not the case. In addition upload queues have been introduced and usually, - and if you are in somebody's upload queue you would not try to download from alternate locations as aggressively as you would without upload queues. So maybe this is another reason for the changed number of upload requests. There's nothing wrong with the program at all. (Well, older versions of LimeWire or other gnutella clients that don't support upload queues will not be able to download from you if there are clients in your upload queue).

And I guess you did not set up your router for port-forwarding, in which case forcing your IP is completely useless. Nothing's wrong. The network has just changed.

I would think that LimeWire set your overall upload limit to a lower value than what you set as "max upload slots" value. It does that at times, when it seems you can't sustain that many uploads.