Did you changed you default storage location settings? What is your Device dropdown shows on the first two entries in Astro? I have found that if you switch the default storage location, the Astro device drop down in the first two entries turn into Internal SD card and SD card (if I remember correctly). Using the default storage setting, my Astro device drop down first two entries are Internal Memory and External SD card. Click on the External SD card shows my external SD card folders and files on the right window.
I did not change anything at all. I basically started from a factory reset, loaded Astro File Manager and noticed I could not access my SD card anymore when I could access it just fine before I let Vizio convert my Operating System to Honeycomb.
You can also use the ES File Explorer to access your external SD card. ES File Explorer when first start will show your internal SD card storage. In my case, it shows /sdcard/ in the top directory entry. To get to the external SD card, you need to click the "up" button. The top directory entry becomes /. Now, select the folder "mnt". It shows two folders with title "sdcard" and "external_sdcard". Select "external_sdcard" will access your external sdcard directory with the top line directory entry showing /mnt/external_sdcard/. You can go back to your internal SD storage by click on the "up" button again and then select the "sdcard" folder. However, this time the top directory line entry becomes /mnt/sdcard/.
I tried exactly what you stated above and all that happens when I press the "Up" is I get the message near the bottom of the screen that says "Press again to exit."
I also loaded PocketCloud because that used to give me a way to access my SD card also and now with Visio Honeycomb all I get when I try to access the SD card in that program is a blank directory.
The only program I know of that I can use to access my SD card is "Gallery" and then all that shows me is what the very first screen of my Videos are and that does not do me much good because none of my Videos have the title of the video in the very first screen.
So the things I lost with the Visio Honeycomb update are: 1. Screen resolution. 2. Flash functionality. 3. SD Card access. and I wish that Vizio would give me a way to put Gingerbread back onto my VTAB1008.