Jenna Jameson -- WHACKED OUT ... Live TV Segment Cut Short Over Bizarre Behavior

Jenna Jameson was a MESS during a live TV interview this morning ... slurring and stumbling as if she was wasted on-air ... and it was so bad, sources tell TMZ that producers cut her segment short.

The 39-year-old porn legend appeared on "Good Day New York" -- promoting her first novel, "Sugar" -- and we're told she was supposed to stay for two complete segments.

But after the first couple of minutes, it was clear Jenna was out of it (at the very least) ... and producers made the decision to cut off JJ before the second segment.

Jenna has struggled with substance abuse in the past .. she pled guilty to DUI last year after crashing her car into a light pole in Orange County, CA. Officials say she had two types of prescription drugs in her system at the time of the incident.

Jenna's ex Tito Ortiz has also said Jenna is hooked on Oxycontin -- but Jenna has denied those allegations.