VOUCHERNUM I don't believe is an out of the box field so I would need to see how you have it defined in Maximo in the Database Configuration application and how it's being set to understand what the problem is exactly. My assumption is you either have code or are crossing over a numeric value and you have defined the data type of the VOUCHERNUM field as a string.
For example, if you had something like this in an automation script:
longvalue=383244
mbo.setValue("VOUCHERNUM",longvalue)
This would throw an error if vouchernum is a string. You can cast the value to a string like:
mbo.setValue("VOUCHERNUM",str(longvalue))
Or get the value in a string to not need to do the cast.