Here the info:
Package: pgfplots 2014/08/04 v1.11 Data Visualization (1.11-3-g4c99d7a)
Package: tikz 2013/12/13 v3.0.0 (rcs-revision 1.142)
I got them from the .log file

It looks like some mathematical error, look the message:

! Package PGF Math Error: Sorry, an internal routine of the floating point unit
got an ill-formatted floating point number `1'. The unreadable part was near '
1'. (in 'ifthenelse(mod(0,2) == 0, 150, 0)').

.
It seems to point to this part of the code:
table [
x index=0,
% because only every second step should be filled
% switch the height of the bar between `ymax' and
% `ymin'. (To fill it the other way round, just
% replace `ymin' with `ymax' and vice versa)
y expr={ifthenelse(mod(\coordindex,2) == 0,
\pgfkeysvalueof{/pgfplots/ymax},
\pgfkeysvalueof{/pgfplots/ymin})
},
]
{data2.txt};