Ginepri, Robredo and Mayer are very beatable.
funnily enough 2 other guys who have an impressive record of losing in the 4th round.
and Malisse. and Boetsch to a lesser extent.
though Gasquet's 4th round record will forever be overshadowed by Juan Antonio Marín's 1st round record - what a absolute legend. I mean seriously, how: http://en.wikipedia.org/wiki/Juan_Antonio_Mar%C3%ADn