Usually if Native mode does not work but Java does, then something is going wrong with the ActiveX plugin.  If you clear your browser's plugins and make sure the DRAC is a Trusted Site with all ActiveX scripts allowed for that zone, then usually the plugin will download and run correctly.  If this still doesn't work, try another browser like Firefox or IE8.
I'm testing a new T320 with an iDRAC7. Management station is Win 7 with IE 9. With the virtual console open I select Virtual Media > Launch Virtual Media. A USB flash drive is mounted on the management station. The flash drive shows up in the virtual media window as drive E and a new drive appears on the managed system named "CD Drive (E:)". If I select the Mapped checkbox for the flash drive, nothing changes in the Details pane, both entries still say "Not Mapped". Likewise the drive contents are not accessible from the managed station. After some digging around it appears this behavior happens when the plug-in type is set to Native uner Console > Virtual Console. If the plug-in type type is changed to Java then the flash can be mapped as expected. So I'm wondering if there is something that can be done to make this work with the native (ActiveX) plug-in type as I would prefer not to use Java.   The image below shows the problem - the checkbox for the USB flash drive is selected but the drive is not mapped, it just shows as an empty CD drive on the target system. [IMAGE]
iDRAC7 virtual media - USB flash drive won't map