Bug#555648: it's a DPI issue...

[Gene Cash <gene.cash@oracle.com>]

Before doing "xrandr -o left"

screen #0:
  print screen:    no
  dimensions:    1920x1200 pixels (507x317 millimeters)
  resolution:    96x96 dots per inch

After doing "xrandr -o left"

screen #0:
  print screen:    no
  dimensions:    1200x1920 pixels (507x317 millimeters)
  resolution:    60x154 dots per inch

Notice the physical screen size isn't properly swapped, and thus the 
calculated resolution is FUBAR.

As another workaround, you can do "xrandr --dpi 96"

-gc

--
Gene Cash       Oracle Support Services (Orlando, FL USA)