Lindsay Lohan -- I Got PUNCHED on My B-Day!

7/2/2010 8:30 AM PDT
Lindsay Lohan's 24th birthday celebration last night was the most painful ever -- because the actress claims she got socked out in a nightclub!!!

It was a madhouse when LiLo and her SCRAM bracelet left Voyeur last night -- but, before she left the club ... she went to her Twitter and claimed she was just "punched" by a waitress ... "for no reason."

Linds was escorted out of the club by security .... but it seems like it was too little, too late.