GSTPST tax rate changes causing errors

We have the following situation that is causing us issues.  On July 1, 2013 Manitoba Provincial Tax rate changed from 7% to 8%.  We made the following changes:

Tax Group = GSTPST

Tax Code = 'MBPST' with rate of 7% end-dated June 30, 2013 and disabled

Tax Code = 'MBPST 8%' with rate of 8% effective July 1, 2013 enabled

Sales Orders created prior to July 1, 2013 had scheduled ship dates equal to prior to July 1, 2013.  Actual ship date was in July 2013.  The trip stops are now failing with "Error msg: Error: Tax Group <GSTPST>, Constraint <Cdn Group Constraint>"

Examples below:

Scheduled Ship Date = July & Nov 2012

order # = 1234

Tax group = GSTPST

tax code = MBPST