There is no glitch involved. The players in that Guild have been inactive for months now. I would recommend seeking out an active Guild and joining them. The Guild board is often used for recruiting. I'm sure there are many Guilds that would be happy to have a Level 50 player like yourself join.
@Sunderland: I've made Rando the Leader because we go by the GXP but Rando can definitely hand it off to Wheaton if that's what your Guild decides is best. Cheers!