Emulator

Game Name?
Mario Kart Wii (Unmodified)
Mario Kart Wii (Wiimmfi)
Super Smash Bros Brawl (Unmodified)
Super Smash Bros Brawl (Project M)
Likely others

Game ID?
Mario Kart Wii - RMCP01
Super Smash Bros Brawl - RSBE01
Super Smash Bros Brawl (Project M) - RSBEC3

What's the problem? Describe what went wrong in few words.
In 4.0-5445 and earlier, any attempt to connect to Nintendo WFC on unmodified games fails with a "cannot connect" error (expected). Attempting to connect to Wiimmfi with a modified Mario Kart Wii or Project M game results in a successful connection.

As of 4.0-5450, doing any of the above results in the following in a "Warning" dialog that stalls emulation and appears to be infinitely repeating.

"Invalid Read from 0x10fd90XX, PC = 0x80004374"

What steps will reproduce the problem?
[Don't assume we have ever played the game and know any level names. Be as
specific as possible.]

1. Start any of the mentioned games (unmodified or Wiimmfi modified)
2. Attempt to connect to online play
3. Observe the warnings

Dolphin 3.5 and 3.5-367 are old versions of Dolphin that have
known issues and bugs, so don't report issues about them and test the
latest Dolphin version first.
Which versions of Dolphin did you test on?
4.0-5445 - works
4.0-5450 - broken

What are your PC specifications? (including, but not limited to: Operating
System, CPU and GPU)
Windows 7 x64
Intel i5 4690K running at 4.5 GHz
AMD Radeon R9 200 Series