I have wrestled with this problem for a while, so thanks for your contributions here, which pretty much resolved it. Exactly the same symptoms, very slow wireless connection after resume from sleep (~ a minute), strange random loss of internet connectivity, during which time I could connect to web sites via a proxy server via vpn (so there was ip connectivity to the outside world), but could not ping web sites, could not connect direct from the browser; then the connection would come back again. Very very irritating. I have four x220s in the family, two had the problem, two didn't.
Bottom line, the netsh commands to disable the hosted network mentioned above worked for my x220, and it has been perfect ever since, resumes from sleep within ~ 5 seconds, never loses the link any more. However, the other non-working x220 had the problem mentioned here, that setting hostednetwork to "disallow" did not work, since in particular after resume from suspend, it would be set back to "allow" again by something. I set up a batch file to run periodically and run the netsh commands, which seems to have stopped the periodic dropout problem, but because the hostedetwork is allowed immediately after resuming from sleep, you still have the prolonged period after resume before network connectivity exits, which is pretty annoying. Also, the batch file had to issue several "disallow" commands in succession, because I had two Miniport adapters, and if you just do it once, one would disappear, then immediately reappear. Having several commands in succession would finally make them disappear, although this didn't fix the problem anyway, since the hostednetwork will still become 'allowed' after resume.
I have finally fixed this one properly, by finding in device manager under 'ports', a device installed by the Intel software called "SOL", Serial over LAN. This is some component of Intel AMT, useless to me, but installed anyway. Disabling this seemed to stop the problem (the hostednetwork still sets itself to "allow", but doesn;t cause any problems). It appeared to be fine just disabling this device, but for good measure I managed to uninstall the "Intel Management Components" from the list of installed programs, and it has gone away for good.
I should also say, in my view this is not a hardware problem; I ran the Intel diagnostics, suspended the computer, resumed, then ran them again; the diagnostics confirmed that the radio was on, several networks were available, but failed because it was not 'associated', which is the part that takes the very large amount of time. So the 'allow the computer to turn this device off' checkbox is a red herring, the hardware appears to be waking up fine.
All of the above is after installing the latest Intel drivers (with none of the optional programs, so just the drivers or so I thought), so my wireless driver is version 15.9.2.1, dated 24/11/2013.
Hopefully this is of some use to someone...
