lime6, is your comp hanging/freezing at any particular time (eg when downloading, while loading LW)? Does it only hang when you've got LW open?

What version of LW & Java are you using? Sometimes, updating your Java will help. Use the offline installer here
http://www.java.com/en/download/manual.jsp

You can also try switching off ultrapeer capabilities (tools > options > speed. Tick 'disable u/p capabilities' & apply). Also, reducing your upload & download bandwidth a bit might help. There's a good guide for optimising LW here, tells you how your bandwidth settings should be for best performance
Configuring LW for best performance
Try reducing the number of simultaneous downloads too, see if that makes a difference