I have what should be a fairly simple validation rule but I cannot get it to work. 

startsWith(WorkPattern="PT") && {self} =="00:00"

i have tried swapping out the && and == for their runtime function versions and it still doesn't work.  the 'starts with' section works when you use it alone but when you combine it with the 00:00 it fails .  Note that 00:00 is the default value shown in the control.  Does this make a difference? Also the WorkPattern field is a choice field.

Help!