@DS127 

"QBO made the huge entry during the conversion and charged it to Opening Balance Equity (the number came from all the $$ adjustment entries on those 1000 products that it put to COGS and OBE. The COGS account came in as a huge negative number."

If QB made an entry to create negative COGS, that must have been a credit entry to COGS.  If it was offset to OBE, then that must have been a debit entry to OBE which would reduce (not increase) OBE as you mentioned.  A JE cannot decrease COGS and increase OBE because both are credits.  There must be another balance sheet account that was hit.