Update: Since posting this I have re-installed Mint from a fresh download as I was having other weird issues (not able to shut down correctly, wouldn’t boot correctly every other time) and all of the problems seem to have completely disappeared. If slow/broken networking is one of your symptoms, your system might just be corrupt in some way or another. The corruption most likely came from a bad install media copy as in my case. I recommend downloading a fresh copy without any interruptions.
I just upgraded to Linux Mint 15 and everything seem to be ok, except I had a weird issue where web pages weren’t loading all of the way, and taking forever to do it. I finally ran across the answer. Thankfully it’s an easy fix, but a weird problem for sure.
Type in in the bottom of the file:
net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.lo.disable_ipv6 = 1
Save and exit. Then run:
Browsing should immediately pick back up. If not, try rebooting.