I'm having problems playing DVDs in Ubuntu Jaunty (9.04); some DVDs work, but most don't. The error message in dmesg is:
end_request: I/O error, dev sr0
All DVD player programs simply freeze after this error.
It is css encrypted disks that causes this error. The solution is to install libdvdcss2, which can be install by first installing libdvdread4, and then running
This will add the medibuntu-repos and install libdvdcss2 and solve the problem.