No- an invoice today, and one created a couple weeks ago (our transaction history goes back to beginning of '11). 
Changes are being made in Method, and the conflict reads:
QuickBooks returned an error when adding/modifying a accInvoice record. 
 The error was: There was an error adding, modifying or deleting 
21ECA-1312839866 because it is already in use.  QuickBooks error 
message: The transaction could not be locked.  It is in use by another 
user..
The Request was: <?xml.
Our office is small enough for me to check that there was no other user (in QB or Method) involved, interested, or even knowledged-in these invoices-- and no reason to be.