UPDATE to my last response - I was WRONG. Adding the rules to field3 did not solve the problem nor does it seem to make a difference whether the checkbox for "Stop processing rules when this rule finishes" is checked or not checked. The ONLY time the rule works is the first time a new form is submitted after the form is first published. Subsequent new forms do not show the month. The Year and Month Number show up, but the Month Text does not show up. The Month Text is set by rules. I have applied them to MonthNumber and MonthText and tried numerous combinations of check/uncheck the "Stop processing...." checkboxes and nothing seems to work.
I am stumped. Can anyone help????????????
UPDATE2: after struggling with this for 2 days I found a better solution -- leaving InfoPath out of the equation entirely. I solved this by creating two calculated columns Year & Month in my SharePoint form library using these formulas:
Year =TEXT(Created,"YYYY")
Month =TEXT(MONTH(Created),"00")&" "&TEXT(Created,"mmmm")
(Note I added the 2-digit numeric month to month name so month sorts correctly).
The beauty of this method is that I don't have to relink existing forms to the newly revised InfoPath form template. The calculated fields appear with their values immediately to all existing forms in the library once they are created. All I wanted to do was group items in the list by year and month. I utilized the built-in SharePoint column "Created" to parse the year and month (instead of my InfoPath form name (string(now())). As a newbie this is an awesome revelation!
Thanks goes to these two posts which helped me set it up:
http://zabistop.blogspot.com/2008/01/calculated-column-to-display-month-name.html
http://www.sharepointboris.net/2009/05/get-the-month-name-in-calculated-column/