Hi all,
I'm having a somewhat related issue using OneWire for DS18B20 temperature sensors no longer working once I create / open a file with an SPI communication routine to my uSD card.
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270923978
I am not using the Libeium microSD module, however. I am using Sparkfun's shield DEV-09520, which is essentially a direct connection between the pins and the SD card. From what I've read about this card being out of spec, I would not recommend it. Also, it is extremely sensitive to type of connector -- only the long legged stackable headers (e.g. Sparkfun's PRT-09280) would work. I could use other connectors and light up LED's no problem, but I could not get a communication signal through them.
I just received a different microSD BOB from Gravitech. Now that I found the stackable headers cured the issue with the Sparkfun boards (on both a Mega 1280 and a Duem 328) for their uSD board, I'll probably wait to try it.
I just need to keep the Temperature Sensors working!