When debugging I can install to the SD Card, but when i make a signed APK I can't

When developing my app I was installing it to the SD card automatically (preferExternal). Then I decided to change this to "auto" and I could still chose to move the app to the SD Card. However, when I put the app on the market I heard that customers couldn't move to the SD card.

I downloaded 开发者_开发技巧from the market and confirmed myself. However, when I run the code using my debug key from eclipse it works fine and I can install to the SD Card.

Why would this be happening?

EDIT:

As requested, here's the relevant Manifest code:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
android:versionCode="1" android:versionName="1" package="package.name"
android:installLocation="auto" android:windowSoftInputMode="stateHidden">

EDIT 2:

I just installed the same APK that I uploaded to the market without downloading it from the market (copied it onto my device and installed) and it allows me to install to the SD Card. This looks like something Google is doing on their market.

Also, I have a Widget in my app, and I know that it doesn't work if you install to the SD Card (hence me changing form preferExternal to auto). Could Google be disabling all apps with Widgets from installing to the SD Card somehow?

Solved it myself.

When you upload an app to the market google checks to see if it contains a widget and if it does, disables installation to the SD card.