I'm using NETWORKDAYS in a scheduling spreadsheet to calculate the
number of working days between two date columns.  The first column (C)
records the date a task was created, the second (E) when the task is
scheduled to be completed.  If the lead time (the difference between
these dates) is less than 3 working days, I want to flag the fact.

The calculation IF(NETWORKDAYS(C258,E258)<3,"x","") works most of the
time, but occasionally there are instances where:
a) there are actually 3 clear working days between the dates but the
above formula returns "x" and
b) there are less than 3 clear working days between the dates but the
above formula does NOT return "x"

Am I missing some subtlety of the function here?