Disable ultrapeer capabilities (tools > options > speed). Disable iTunes sharing.
Don't download too many files at once, keep it to just a couple, & don't resume many incomplete files at once.
Reduce your upload & download bandwidth a little bit.

Update your Java by downloading the JRE offline installer here (remove your old Java version before installing the new one).
http://java.sun.com/javase/downloads/index.jsp

Can you give us a few more details? Sorry for any repeat questions.
System details - help us to help you