Lindsay Lohan BLOWS OFF Voiceover Session -- Ripped By Screenwriter

Lindsay Lohan screwed up again ... no-showing at an important voice-over session for her upcoming movie ... and now the screenwriter is BLASTING her for being a flake.

Bret Easton Ellis -- who wrote Lindsay's new flick "The Canyons" -- claims Lohan missed her Automatic Dialog Replacement session on Wednesday ... and posted a tweet, saying he sent his bloodthirsty character from his 1991 book "American Psycho" over to find her ass.

Here's the tweet -- "Patrick Bateman has just headed over to Lindsay Lohan's hotel to confront her as to why she missed her f**king ADR on 'The Canyons' today..."

Of course, punctuality hasn't always been Lindsay's strong suit ... she has a history of running late to things like movie sets, made-for-TV-movie sets, "Glee," court dates, community service, airports, alcohol education classes, birthday parties ... and lunch.