I actually have some of the same issues. I have a 13' MBP (not retina) and I have had it since August. Recently (definitely AFTER updating to Mavericks), I have experienced all my internet browsers to just stop working after awhile or just be stuck loading forever and it will load eventually sometimes. I have learned a couple of ways to temporarily fix it such as resetting safari (Apple customer service told me that one), restarting completely, and emptying caches on safari or whatever browser I am using. I know it is not my internet because my Twitter app works perfectly with the internet, just my browsers. I am sick of dealing with this and needing to pause my internet surfing just to reset everything! So if anyone knows what is going on with both of us, please let us know!