|I see that someone else suggested going through the security settings on your router and enabling the highest level of password and encryption which is always a good idea.|
You mentioned the fact that your logs show that a neighbor is abusing your router and sucking on your bandwidth, I'm curious to know whether that was enough -- mentioning it -- to motivate the neighbor to refrain from doing so any longer.
The fact that you informed the individual(s) that you're aware they accessed your bandwidth should, I would expect, drive them to refrain at least for a little while. }:-}
Did informing them help? Did you set highest encryption?
Also there are open-sourced products that typically run under Linux which cracks WAP and others, products such as Air Snort. Do you know if your neighbor(s) utilize Linux?