Re: Activating mobile data for goole services was the solution in my case
Ah, maybe that's what's behind those mysterious failures... People turning off mobile data access specifically for Play Services to save battery / traffic. Can't blame them, but this made the issue quite puzzling for me.
But maybe that's not the whole story, and "genuine" failures can happen too.
1.6.0.2-2 from last night uses an updated version of Google Play Services library (8.* vs. 7.* in previous AquaMail versions), maybe it'll help, but really who can know...