You probably could have a corrupt message board. Hold + and - at the health screen, then push A while holding. If your system menu loads, do this-
download Det1re's Mailbox Brick Fix.
1. Copy "apps" and "fstoolbox" to your SD card root and overwrite if asked.
2. Startup the Wii and boot HBC (you can use BootMii, Preloader or the Maintainance mode)
to do so.
3. From HBC, run FSToolbox r50 and follow the on-screen instructions until you see your
Wii's file struct (import, meta, shared1, shared2, sys, ticket, title, tmp).
4. Navigate to shared2/wc24/ and replace any file with the one from SD by pressing PLUS.
5. Navigate to shared2/wc24/mbox/ and do the same there.
6. End the app and restart the Wii. You will get a message that your Mail account is broken
and will be restored.
Doing the steps above will remove all your saved friends and all messages from your
If that does not help, try a system format.
You may want to backup your saves first.