Hi,
Do not delete the post, as others may have a similar problem
I have uploaded a firmware that correctly works with a general 9V battery. My firmware have a section for microSD writing and with the general 9V battery it correctly works.
What firmware?
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
How are you connecting the 9v to the Arduino?
Tom... 