When an approver is finalizing a requisition, they may receive Internal Error when clicking to finalize. This occurs if when creating the requisition, they received the warning "One or more accounts are over budget. If you do not correct this situation before saving this record, these budgets will be exceeded. Do you want to proceed?"
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.