Yes, download the linked file above on the windows machine.
1.
-Connect smart card reader
-Go to (Start | Settings | Control Panel | Administrative Tools | Services) and stop the following services:
ActivCard Gold AutoRegister
ActivCard Gold Service
Smart Card Service
-Extract the SCRx31CCID_FW_V5.18.zip file and run fwupdate.exe
-Select OK and then Browse and select the SCR531_V518.bin file and select Open
-Select Next and verify that the new firmware value is 05.18
-Select Finish and then Close
This will flash the activcard to an SCx31 and it will be usable on your Mac.
It will take about a minute to flash and it will be usable on both windows and OSX.
2.
From there plug it into the Mac and insert your CAC. Open keychain access and see if your CAC is listed in the top left. If so you are on your way.
3.
Get the DoD certificates. I can't help you here, but if you use a the reader/CAC on the windows machine I think you can download them here:
http://dodpki.c3pki.chamb.disa.mil/rootca.html and then copy them over to your Mac. Install them on your Mac-- Double click them and they will go into your keychain access.
4.
Now follow this to access .mil (in safari)websites as the
root URL must be associated with your certificate to ask for your PIN.
http://support.apple.com/kb/HT1679