It's a speed cap. Speedtest.net gives me this from the closest server:
I only ran the test once so these results are not set in stone.
One weird thing just happened; I disabled windows firewall and was then able to enable UPNP in game which I wasn't able to do before. Still get the same error message though.
These are the ports I have forwarded on my router by the way:
TCP 3074 - 3074
UDP 3074 - 3174
TCP 10130 - 10130
UDP 10140 - 10140
TCP 80 - 80
Update: I got it to work! It's definitely the cap that is the problem. The other day I noticed when I was downloading R6V2 through Steam that if I restarted my router it was as if the cap was lifted for a short time, giving me much more speed (up to 1 MB/s) which made the download process jump up about 3% before going down (to about 24 KB/s) again. So I restarted the router, brought up the game, hit login and it worked almost instantly. Yay!