parseDate cannot parse ISO8601 dates produced by FastDateFormat

I cannot see why this is failing but here is my code:

Date parseDate(String dateStr) {
Date d = null;
if (dateStr != null && ! "".equals(dateStr)) {
try {
// try to parse the date from ISO8601, general
formats, and RFC-2822
d = DateUtils.parseDate(dateStr, new String[]

{ DateFormatUtils.ISO_DATETIME_TIME_ZONE_FORMAT.getPattern() }

);
} catch (ParseException e)

{ // nothing to do log.info("Failed to parse: " + dateStr + ":" + e, e); d = null; }

}
return d;
}

The string I am sending in to that method was generated like this:
String isoDateStr = DateFormatUtils.ISO_DATETIME_TIME_ZONE_FORMAT.format(date);

The exception is:
2009-09-03 13:29:37,644 [399355530@qtp3-2] INFO
search.SOLRSearchService - Failed to parse:
2009-09-03T13:29:30+01:00:java.text.ParseException: Unable to parse
the date: 2009-09-03T13:29:30+01:00
java.text.ParseException: Unable to parse the date: 2009-09-03T13:29:30+01:00
at org.apache.commons.lang.time.DateUtils.parseDate(DateUtils.java:285)
at org.steeple.impl.search.SOLRSearchService.parseDate(SOLRSearchService.java:412)
at org.steeple.impl.search.SOLRSearchService.execute(SOLRSearchService.java:311)
....