This is a known bug in the Adafruit BMP085 library.  
You can follow the discussion and the bug fix process in the Adafruit forum:   
[Raspberry Pi and the BMP085][1]  

GitHub issue: https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/issues/38

Thanks for all suggestions!

UPDATE: Adafruit released a new official python library: https://github.com/adafruit/Adafruit_Python_BMP


  [1]: http://forums.adafruit.com/viewtopic.php?f=8&t=38255