The staff member reports an error
"cast to numeric type on NULL value"
when creating a new account from PCP/RCP. Further attempts to reproduce an issue fail - accounts are successfully created, no exceptions.
Most probably the staff member used the browser button "Back", probably several times (WWW.log and apache logs can confirm it). There is a bug about browser button "Back" causing exceptions - #PBA-66250 ("Clicking "Back" browser button several times causes an exception "cast to numeric type on NULL value" when creating an account").
Do not use the browser navigation buttons, especially in wizards, where some data is cached and some not.