I have an inexpensive all-in-1 card reader plugged into the Raspberry Pi and shared with virtualhere server 1.5.1. I am running the latest client on Windows 8 (1.6.2). I can see the device (shows up as USB Mass Storage Device, as expected) and can click & use it however none of the cards plugged into it are mounted. I have confirmed it works as expected when plugged in locally.
If I plug in a regular USB flash drive and share it then it is mounted and works as expected.
Is there any additional info I can offer to troubleshoot?