If locale is set to "fr_FR" parseRFC822 fails.
For exemple :
trace(DateUtil.parseRFC822("Mon, 02 May 2011 08:53:37 +0200"));
"Thu Dec 2 07:53:37 GMT+0100 2010"
I think the problem is in DateUtil.getShortMonthIndex, it is locale dependent so it fails if non english locale is set.
Maybe it shouldn't be local dependent as it is intended for loading RSS feeds where the date is always in english ?
I created a fork where the locale is ignored (always english) for DateUtil.getShortMonthIndex if that can help someone: