From the original announcement:
"The characters which can be used now are listed on the following two pages:
http://msdn.microsoft.com/en-us/library ... .110).aspx - 'standard' strings
http://msdn.microsoft.com/en-us/library ... .110).aspx - 'custom' strings
If the string contains only one character, it is regarded as a 'standard' string, otherwise it is a 'custom string'. This does mean that sometimes you will not be able to uses a 'standard' string, but there should always be a way of achieving the same effect using combinations of 'custom' strings."
You are trying to use 'standard' format characters in a string which is more than one character. You need to use 'custom' format characters, e.g
<#MonthMaxTempLD format="'at' h:mm tt 'on' MM/dd/yyyy">
will give you a US format time and date.