Moroccan men seem easily able to reach slam quarter-finals, but get no further.
Both Hicham Arazi (1997, 1998 FO; 2000, 2004 AO) and Younes El Aynaoui (2000, 2003 AO; 2002, 2003 US) made it to four slam quarter-finals without winning one. In El Aynaoui's case, he played the longest slam quarter-final of all time at the 2003 AO against Roddick, losing 19-21 in the fifth, before succumbing to the Moroccan curse.
Not convinced? The curse has affected even those men who were born in Morocco, but have represented another country: Guy Forget, as a Frenchman, lost in five quarter-finals (1991, 1993 AO; 1991, 1992, 1994 W), while Ronald Agenor, as a Haitian, lost in one (1989 FO).
That's a total of 0-14 for Moroccan-born men.