You aren't alone. My Wii U and 3DS have been giving me similar error codes when I check my friend list.

I couldn't get on here for a bit either.

Did you get 001-0502 or something like that? i got it once and it went away after a while. You can also fully re-Install Nimbus.

My 3DS is doing fine now, but the Wii U is still acting up.

Oh, and my Wii U has been on the Miiverse loading screen for about 4 minutes now. Servers might be overloaded again.