The email client of this problematic message is IncrediMail. The company editing this software should be alerted of the problem. I didn't know what IncrediMail was before.
Instead of doing a
var_dump( strtotime('Sun, 24 Oct 2010 21:11:15 +0200 (Paris, Madrid (heure d\'été))') );
could you rather do a
var_dump( strtotime('Sun, 24 Oct 2010 21:11:15 +0200') );
and delete everything between brackets when there are some ?
By the way, "heure d'été" means "daylight saving time". It is probably something that did not need to be translated in the software and should remain in English.
Concerning the problem of mailing list rules deleted during the update, it's weird that you did not succeed to make this problem happening again from your side. Did you try with 2 rules instead of just 1 ? And did you apply the patches that I had on my 3.0.1 installation before upgrading ? They are patch 5010 (Add Mailing List importing over POP3-SSL and IMAP-SSL) and patch 5014 (Fix duplicate headers when posting forum posts to a mailing list). Hope it helps.