In Ext4 file system, Delayed Allocation causes some extra risks of the data loss if your system gets crashed before all the data is written to hard drive.
This was also covered on slashdot over 2 years ago.
It appears that the transition to Ext4 requires applications properly use fsync() to prevent data loss. Theodore T'so, who played a major role in developing Ext4, includes a good summary here. In fact, Android devices which run on Ext4 are rolling out and preventing data loss has been a major concern.
I can't imagine the Open Office that ships with Ubuntu 10.10 doesn't adhere to the Ext4 spec and use fsync() properly but I've never had this problem in other apps. Very aggravating and perhaps another reason to use Google Docs or give Libre Office a try!