I was having some issues with this app, like many of you. I updated my app, and somewhere along the line I started receiving the "invalid data" error. This happened so long ago, I don't know exactly what caused it, but today I was determined to get this app working.

I uninstalled the app, and reinstalled it to start fresh. I went to add my blog, typed in all the required fields...and the app crashed. I reasoned that well maybe it has a problem with small passwords, because my password was 6 characters and simple, so I changed it.

I re-entered the required fields again, this time no crash...but it did say that the app was "unable to read the wordpress site on that url". I double checked and verified my XML-RPC was working properly, so I couldn't figure out why it was having this issue.

Up until that point I was using my site's URL minus "www" when entering it into the app, because we have it set to remove it anyway. This time I decided to add the "www" when I entered in the url and TA-DA it worked.

tl;dr
- If you updated the app from a previous version, reinstall it.
- If it crashes when you try to save your blog, change your password.
- If you have your domain setup to remove "www", add the "www" when entering it into the app.

Hopefully this information will help someone else out. :)

Thanks!