After updating Small Business Accounting to SP2, I found that I could no longer export an invoice to my custom template as I did before.  I would just get this error message in a dialog:

OLE received a packet with an invalid extension

To resolve the problem, I (eventually) opened my custom invoice template for editing, then closed it without making any real changes.  When the dialog asked if I wanted to save changes, I clicked 'Yes'.  After that, exporting to my template works just like before. 

I'm assuming the template had to be updated with the new fields that SP2 allows in templates...the memo field is the only one I can recall reading about at the moment.