Invalid hexadecimal or binary string

Synopsis
What was supposed to be a numeric expression in your script contained non-numeric characters (ie, not '0' to '9', or if hexadecimal 'A' to 'F' as well).

Cause
You supplied the numeric expression from a variable, and that variable has non-numeric characters as a result of concatenating it with some expression that also had non-numeric characters, or assigning it a literal string containing non-numeric characters.

Cure
Do not do something like the following. This turns the value of My_Variable into something that isn't purely a numeric expression (because the whole expression is supplied in quotes, meaning that it's a literal string, and it contains a non-numeric character -- a plus sign), Numeric expressions must use only numbers (and 'A' to 'F' is hexadecimal).

My_Variable = '10 + 5'