POOR LINDSAY

SAMANTHA RONSON DUMPED LINDSAY LOHAN AGAIN . . . VIA TEST MESSAGE:

It's over . . . AGAIN . . . between LINDSAY LOHAN and SAMANTHA RONSON. (--Sam and Lindsay first broke up in April . . . but they got back together last month.)

Samantha reportedly dumped Lindsay Monday night, following a huge argument that started over . . . NICOLE RICHIE. Sam is good friends with Nicole . . . and Nicole HATES Lindsay. So that was already causing some friction. But last week, Nicole invited Samantha to a party . . . and told her she couldn't bring Lindsay. Sam went to the party, and Lindsay went DOG NUTS.

On Monday night, Sam and Lindsay went at it pretty seriously . . . then Sam went off to dinner with Nicole. After dinner, Sam broke up with Lindsay via TEXT MESSAGE . . . and told her it was over for good this time.

By the way . . . Here's a quick update on that Lindsay Lohan jewel heist nonsense: It was actually $410,000 worth of bling that was stolen from that "Elle" magazine photo shoot in London. But "Elle" says Lindsay is in no way a suspect . . . and, for the time being at least, it doesn't look like Scotland Yard is interested in interviewing her.