HiI can confirm this, for text files too. If I try to open a text file of an odt file and there is no extension on the file name, nothing happens. This is the same whether I try using the OpenOffice open dialogue or from Nautilus. If I rename the file with the appropriate extension it opens normally.
I have reported this upstream: http://www.openoffice.org/issues/show_bug.cgi?id=104706
John