I have the same problem: extrapack fails install near 90% mark. I'm also on an Ouya running the latest Gotham nightly. My Ouya is rooted. For some reason Astro File Manager only works for me (aside from FilePwn but that can't access root system files). Here is what I did (but this is still not working for me... any help appreciated):
I downloaded skin.aeonmq5.extrapack.zip using my dropbox account to download into the download folder.
I launched Astro File Manager and went to find the directory Wanilton points to above (Android/data/org.xbmc.xbmc/files/.xbmc/userdata/addon_data\) - I could only see an Android folder under "/storage/sdcard0/Android/" it had "/data" and "/org.xbmc.xbmc" sub-directories but was empty.
I tried creating a ".xbmc" subfolder (with the period in front as Wanilton shows in his path above but I couldn't create it. Thinking this was a name error I created a folder called "xbmc" (no period) and then continued creating the rest of the pathway.
So my pathway is/was: "/storage/sdcard0/Android/data/org.xbmc.xbmc/xbmc/userdata/addon-data/"
Then I moved the zip from the download folder into my new pathway, and extracted it. (Got a null error, however everything looked good/looks good and extracted).
Re-launched XBMC went to settings for the MQ skin and none of the theme pics etc were available/showed/worked. So I tried to download the extrapack from within the settings/skin screen again in XBMC and still get a "failed" at around 90%
Here's the strange part - I went back into Astro File Manager and tried to rename the folder "xbmc" to ".xbmc" and got a prompt for a directory conflict and realized maybe there are invisible folders/files that Astro isn't showing me (including the .xbmc I couldn't see and the reason I couldn't create that folder in the first place). Trying a "merge" didn't work ("Conflict Copying" error).
Anyone have a suggestion or know if Astro File Manager can display hidden files? (Is there a setting?) Many thanks, and sorry for the lengthy post!
Oops. Apologies. NM. Answered my own question. Indeed Astro File Manager defaults to NOT show hidden files and you have to turn this ON in settings. Once you do... voila... there is the ".xbmc" folder and the whole shebang.
Sorry for that.
I'd have deleted the post above if I could have.
Maybe it might help someone else.