Jessica Simpson -- NOT Drunk on HSN

Jessica Simpson wasn't drunk during her HSN debut and you'd know that if you watched the entire two-hour segment ... which would be more painful than eating glass.

Sources close to Jessica say the clip circulating of her giggling and slurring is just part of her personality that surfaces from time to time. They say for the lion's share of her time on the show, she was lucid and polished.

They say 2 hours without a script creates inevitable less than perfect moments.

An HSN source also says she was not drunk.

Fact is ... HSN is singing her praises, saying Jessica really knows how to drive a sale.