If you are, and you are using Gmail with POP service, drop out to the web interface for Gmail and login to your account. Gmail seems to be having some periodic problems with corrupted email accounts. There is nothing publicly reported yet, but I'm sure there will be soon.
For the time being, if you are using Gmail for the email lists, and can't wait to participate, use another online account such as Live or Hotmail for the lists.
BTW: This only affects some people currently. It seems to be pretty intermittent right now, but the number of affected users is growing daily.