That's a great response. I have my router configured at home as N only, but the guest one at work is N/G. I get the same problem in both locations. It work work fine then boom, I would tap on something in the store, twitter, web page, what ever, and it would eventually say something to the effect of not being able to connect to the internet. If I try and play Wipeout it will eventually kick me out of the lobby, saying it lost connection. I have a G router I connect to at work and a spare G router at home now as well to get my by till this problem is patched. This is also my second Vita. I took the first one back thinking it was defective.
While I have never been "kicked out" I have seen my Vita disconnect from the network. I thought it was a battery saving "feature." I have not run into any issues with it connecting to PSN, the web or even EA's online gaming site.