I'm doing my head in with this one.

On my home PC, whenever I switch user (doesn't matter which accounts, switching between any two accounts causes the same problem) the internet connection dies completely until a restart. I've turned the WiFi power saving mode to maximum performance and manually unchecked "allow Windows to turn off this device to save power" in case there was something strange going on with power saving, but it hasn't helped.

What's really odd is that Windows reports the wireless adapter as still being enabled and connected, although when this happens I can't communicate with the router, suggesting the whole network connection is dead (it hadn't occurred to me until just this second to try remoting in from another PC to verify this, though if the PC can't connect to the router's admin page it seems likely no network facilities are going to work)

Has anybody seen any issue like this and more importantly, found a solution?

I'm using the built in wireless adapter of my ASUS P8Z77-V Pro mobo. I do have a spare WiFi card somewhere, but I'd rather not waste a PCIe slot if I can help it!