I don't see it, mostly because I think you and others overstate the errors situation. The Sox lost last night because Verlander had an excellent game--6 IP, 9 K's, 0 runs--and Houck was just OK. We lost both games to the Astros because their hitting and pitching were both better than ours.
The errors, I agree, were/are infuriating, but not game deciders.
Tonight I believe that, as was the case Monday and Tuesday night, hitting and pitching will be the difference. I think Sale vs. Urquiddy gives the Sox a big edge. However, I have my doubts about the Sox hitting, especially the lefty bats--specifically, Dugo, Yoshida, Duran (on the DL), and Casas--who should be given the Sox an edge against righty starters.
Back to the errors, including the mental ones. They may in fact reflect the current mindset of the whole team, including their manager.