I use OS X.
I had the same trouble with the last update and had to wait the 45 days for it to be installed automatically. Nobody at Adobe seems able to solve the problem and nobody seems to care. If I could use something else I would.
I have tried all my passwords including my OS one which works perfectly on my iPad.
This is the OS (Apple/OS X) prompting for the password, not Adobe/Flash Player. Normally this is the password you use to log onto your system, which may or may not be the same password you use to log onto your iPad. Please review the FAQ Varun links to. It contains several links to Apple tech notes for assistance in troubleshooting password issues.