Upgraded macbook to 10.8.3 and network is broke

As the title says really.

Upgraded to 10.8.3 and everything seemed ok for a couple of days. Then a couple of days ago the internet started going really slow, and today the macbook doesn't seem to be connected to the local network even though the wireless indicator shows it's connected ok.

I've tried rebooting our internet connection (router/modem), all other devices in the house are ok (iMac, 2 iPads, 2 iPhones), it's just this Macbook that seems to be having the issue.

I've deleted the Airplay stuff from the keychain, but it didn't seem to resolve anything.

Does anyone have any ideas on how to resolve this issue?

 

Yep, numerous times.

I disconnected from the wireless network earlier, re-connected, and the network/internet started working again, but after a few minutes it stopped.

 

One other thing.

We have two user accounts on the Macbook, a standard user account works fine, but it seems to be the administrator account that's having the problems.

I'll try the disk permissions.

 

Repairing the disk permissions didn't fix it.

 

I kind of fixed this.

Tried all sorts of things, resetting the vram, removing the network from the keychain. Reducing the router to use slower wireless, none of it worked.

Went into the garage, got an old router, plugged it into my existing router, disabled the DHCP and connected the iMac to that instead. Bingo, working.