If you've only used LW 4 in the past then you'll find that LW 5 is very different. The FAQ & User Guide will probably give you some idea.
User Guide - LimeWire
LW 5 FAQ - LimeWire

The latest stable release is 5.2.13: Official Website & Free Download - Lime Wire

There's a Beta version available as well: LimeWire Forums

You can check out the changelog to see what's new in various versions: Changelog - LimeWire

If you want to stick with LW 4 then 4.16 is probably a better choice than 4.18. This thread has more info & a link to download: Downgrading to LimeWire 4 from 5 & resuming incomplete downloads

If you want to find out what people think of LW 5 compared to LW 4 & problems that they may have had - use the forum search to look for update problems, problems update or something similar... there are a few threads around with info