Mac Mini SD Card Reader not working

I have a recent (2 month) old Mac Mini purchased directly from Apple. It has the integrated SD card reader. The reader worked fine initially but then just stopped working. I'm not sure if the problem started after a software update. I updated all the software just now and it still does not work. I'm using SD Cards of various brands - none work and they use to. If I connect my camera via a USB cable - Iphoto launches and all works fine to upload photos.

Is there a way to test the Card Reader? Is there a way to see if the driver is installed and working? This is my first Mac so please kept it simple and make no assumptions about my knowledge of the OS!

thanks