Hi -
So, my guess is you are using the SubmitToSharePointList command. Is that correct? And you aren't using the /id parameter?
We had a little bug in the browser in a previous release of version 4.1, if that is the version you are using - and it is fixed in the download currently available.
However, from your final question, it sounds as if you need to be using the /id parameter. If you include that, qRules will be able to update existing list items instead of just adding new. Since you are submitting repeating data, simply add a node to your repeating group for storing the id from SharePoint. Name it id, or ShpId, or whatever you like, and then add the id parameter to your SubmitToSharePointList command:
/id=my:ShpId
Replacing the bold type with the actual relative path to your new field.
For a form where you aren't submitting repeating data, you'll use the full path to the new node you've added for storing your id - just right click the field in the data source task pane in InfoPath, and select Copy XPath. Then use that:
/id=my:myFields/my:whateverTheGroupIs/my:IdFieldIJustAdded