After upgrading, you get the following error message in the Account Maintenance window.
Error registering trigger Field_Pre_Generic_Trigger for 'Account Number' of window 'GL_Account_Maintenance' of form 'GL_Account_Maintenance'. Error code 4.
As of Version 9.0, Dynamics GP changed the name of the Account Number field to Account Number CS.
Open the Audit Group you use to audit the Account Number field. Open the audit and unmark the Account Number field and mark the Account Number CS field instead.