I have two wifi USB adapters ( One from Belkin and another from Netgear) which had the same limited connectivity issue. Both the adapters are Realtek based.
I read somewhere online that the issue was restricted to 11n. Now I don`t know how this makes sense , but restricting my USB adapters to work in 802.11b/g mode only, works for me. You can change this setting in the device manager .
I`ve tried all the other solutions mentioned in this post and elsewhere(including reverting to older manufacturer provided drivers) but none have worked.
So right now my working setup is : older driver( as mentioned in other posts) + disable 11n mode in the adapter ( for me it doesn`t make much of a difference in link speed)
Some pics to help.
1. Setting in device manager

- Pings look normal - ( i used the ping to AP as a metric to see how my adapter performed)

- I change the device mode back to 802.11b/g/n and this is what I see
The initial "PING: transmit failed" messages are when I`m changing the mode ( the wifi connection is disrupted during this process)
And then the typical "Request timed out" messages start popping up - just like they used to before.

In 802.11 b/g mode , Ive had ping running for quite some time now and seen no issues. Will update the thread after a few days if my fix still works. ( the driver rollback fix had similarly worked for me for a few days and then the issue cropped up again. Hence not taking this as a final solution until Im sure)
The current drivers I`m using :

Let me know if this works.