This type of error occurs when Proclaim tries to populate a field selection with more than 32000 bytes (characters).
Usually when you have a list behind a dropdown/browse field that has options, such as selecting fee earner/nominals this can be anything that might have an option list to select from in either Proclaim Case or Proclaim Accounts.
Please raise a new case online and reference the title of this article, also if you can provide a screen image of the error and which screen the error occurs to help us investigate.