I had migrated all our moodle site from version 1.9 to 2.2.1+ successfully. Though I encountered some plugins not able to upgrade and I remove it from the system then pressing couple of refresh and it went fine. BTW, my moodle site are running from IIS7 + PHP under in Windows 2008 server.
Now the problem in the upgraded moodle site is that when I try to download any PDF files in the courses, the error message pop up of "File does not begin with '%PDF-'". I checked the pdf file in the webroot moodle data (datadir) location and found its working or not corrupted. I can able to open the pdf files. I have no idea why all pdf files are corrupted. I've been focusing this issue since last week and still no luck to fix it.
Any help from you guys would be much appreciated.