I've done this with a Rep Table straight out of the box. Seems to work fine. SP 2010 and InfoPath 2010, browser version : IE 10 - add-in free.
The only thing I can think of is to create a RepTable in a web part page straight out of the box.
Does it work deleting a single row? Then customize the table commands, add the Remove All command, republish and test again.
Make sure you change the command name, so that you know you're deleting what you should be deleting.