Getting EDatabase Error randomly while executing VBScript code

While doing this, I am getting the below error randomly. 

While doing what?  You didn't show us any code.  And how often is "randomly"?  Every time, every other time, once a week?

Error Invalid value for field 'Sales Area'

Is all your data valid?  Check the row of data where the failure occurred and make sure "Sales Area" has a good value.  Try a simple query that would give you this row and display "Sales Area" and see if that fails.