This may sound strange, but I live on the end house of 3 and our neighbors are good friends now.

There is one issue though. The neighbor 2 houses along is a genius programmer with Linux and MAC based tools and I am certain that he is hacking my computers via my Linksys Cisco wireless router.

I have set and secured the Linksys router with both a WPA2 key and IP lookup username and password.

I let my neighbor use my main computer the other day (Window 7 based) and he did a CMD 'IPCONFIG' when he thought I wasnt looking, so he probably has my direct IP now.
Now all of a sudden, applications crash to windows and I notice my network monitor and hardware going haywire sometimes.

I am sure that the average user wont be able to hack my network, but this guy develops software for a living. Even though he's a friend, i don't want him nosing at our (My fiance and I) holiday pics etc.

Is it possible to physically block a signal from the direction of his house using materials etc? The mrs uses wireless for her laptop but I am hard wired to the wireless router. (I dont want to have to hard wire everything)

Any help greatly appreciated!!! Thank-you in advance.