Crappy Statistics
 

Under my Statistics window I get:
Total Messages: 498,124
Routing Errors: 306,468
Dropped Messages: 310,249

I don't think I'm an ultrapeer. I'm behind a NAT/Firewall.

Anyways, these stats seem very bad!
61% of my messages have had routing errors
62% of me messages are dropped

What does this mean? are all the ultrapeers I'm connecting to overloaded?

Well, that many dropped messages are quite usual and nothing to worry about.

As for the routing errors - they are normal, too. Although I don't have that mayn (more like 30% of the total messages). - Were you connected to any non-LimeWire ultrapeers?

currently my ultrapeeps are:
LimeWire 2.1.3
LimeWire 2.4.2
LimeWire 2.2.4

It was just a guess. But you shouldn't worry about the statistics, it doesn't contain much information anyway.