How can I mount a USB flash drive on my Acer Iconia? I have an Acer Iconia A500 tablet with Android 3.1. I cannot mount any USB flash drives. File Manager HD and other similar apps display "Directory is empty" in /mnt/usb_storage/. I have tried use a flash drive formatted FAT32, and my USB port works (I've checked with a USB mouse).  How can I get this to work?
You have to use File Manager HD and do the following Steps : 


On the panel at the left tap Storage.
On the panel at the top right press the Up arrow until the first directory entry is asec. 
Now scroll down through the directory and you should see usb_storage. 

4.Tap usb_storage and you should see your data.


Hope i will help. 

From : http://androidforums.com/acer-iconia-tab-a500/358421-iconia-a500-cant-browse-through-usb-flash-drive.html