-Reason for breaking up: not entirely clear (obviously one-sided). Something about stagnation and inability to see it ultimately working out. Apparently it "didn't have anything to do with me," but that's usually a load of crap.
-Basis for getting back together: see previous answer. Didn't really see a need for it to end, so if the ex can get over their own issues, then all the original bases for being together are still in place, as far as I'm concerned.
-Residual attraction? Definitely. Basis to build a relationship? Still intact, from my POV anyway. Previous issues still present? Didn't really see any, but again, this depends on the ex. Hard to get the ex to take me seriously again as an option, though, and keep my self-respect intact.