I got burned by this recently so I thought I would share this to save you some time.
If you export a budget from Dynamics GP 2013 (and presumably earlier versions), Excel is not required on the machine. As a consultant I often end up with remote access only to the SQL Server. If GP is installed, I can still export a budget, save the Excel file, and move it to a different computer to work with it.
Exporting Analytical Accounting based budgets does not work the same way. With AA budgets, Excel is REQUIRED (though this isn’t documented or listed in a KB) on the machine performing the export because the AA budget routine opens the budget spreadsheet when done. If Excel is not installed on the machine, GP throws the helpful error:
Unhandled object exception:
Invalid class string
EXCEPTION_CLASS_OBJECT_EXCEPTION
ExceptionSubClass:-2147221005
Hopefully, Google and Bing will index this now so that someone else won’t get stuck trying to hunt down this error.