I had my laptop replaced recently and when I tried running an AIR app I was working on I received a message indicating HTMLLoader.pdfCapability == ERROR_INSTALLED_READER_TOO_OLD when loading a PDF. The machine has Adobe Reader X. I read elsewhere that deselecting "Enable Protected Mode at startup" in the General Preferences of Adobe Reader would solve this problem. It didn't work for me....anyone have other ideas or suggestions? Prior to receiving the new machine this worked ( probably had an earlier version of reader though).
The reason I was getting this error message was due to Debugging the application from within Flash Builder. Running the application after installing it from an Export Release Build resulted in the PDFs loading correctly.