From the Microsoft Dynamics NAV Blogs: RTC for Excel Import, Managing Network Files, PDF Reports; Partner Assistance
Import Budget into Excel in Dynamics NAV RTC: Alex Chow recently commented on this subject in his blog "Confessions of a Dynamics NAV Consultant."
According to Chow, when you're working in the RTC environment in the G/L Budgets, the standard NAV function lets you export the Budgets into Excel, edit it, then import it back in the same Excel format. This works fine in the classic client, he says. But when you try to import the budget in Excel in the RTC environment, you get this error message: dates have not been recognized in the Excel worksheet.