I guess it depends how old your previous version was. For windows one version works well for one person & not another, then next version it can be vice versa. The best I can suggest is these tips: Tip: Purge the Downloads Queue! which was intended for mac but also applicable to windows users in principle. I can assure you it makes a big difference!

Perhaps also with the newer version LW, try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.)

BTW come to think of it, it was said to me by a dev that some incompletes from older versions might struggle in the newer versions. But that was a while ago (ie: after LW 4.8.1 due to a no. of changes in the internal LW engine so to speak.) But after updating that newer downloads & incompletes would behave much better. I'm not sure what difference this makes with LW 4.12