String length is less than 0 or not an integer!

[vlad2]

the behavior of the report is really viard just yesturday this reports run perfect but totay report crashes.whith the message: 'String Length is less than 0 or not in integer'

i guess i have bug or incorrect data in DB.
What might cause the problem?

thanks in advice...

 

[Ngolem]

you probably have null data and not testing for nulls in your formulas...perhaps it is in a formula that converts a string to a number...but that is just a guess