Patrick:
Did you check that the SD card was no larger than 2 Gb and formatted as FAT16?
Since you could flash OpenLog with the Arduino sketch, you were almost there.
To reflash OpenLog follow these instructions:
In the directory containing the OpenLog object file (main.hex), create a batch file “flash.bat” containing the single line:
C:\arduino\hardware\tools\avr\bin\avrdude -p atmega328p -P COM1 -c stk500v1 -b 57600 -CC:\arduino\hardware\tools\avr\etc\avrdude.conf -U flash:w:main.hex
In the above make sure that the COM port is correct (it is almost certainly not COM1), that flash.bat and main.hex are in the same, default directory and that the location of avrdude is correct. Open up a DOS command line window, set default to the directory containing main.hex and flash.bat, and type flash
To use your newly reflashed version of OpenLog there is no change in the connections. Run hyperterm and connect it to the correct COM port, 9600 baud, 8 bits, no parity and 1 stop.
Type ^Z to stop logging and away you go.