It sounds like a physical hardware problem, not software. If you played it once and there is no apparent physical damage to the disc it may be a problem with your disc drive. If you can, try playing it on another piece of hardware like a dedicated DVD player. Also, you could try playing a known good disc (that you don't mind losing) in your PC drive. This will help narrow down the cause to either the disc or the drive. I've had more drive failures over the years than disc failures. The discs that did fail were usually writable discs or obviously damaged. Most of the damage looked liked scratches of the read side or label damage.

Does it play on standard DVD players? Is it a pressed copy (silver) or burned (typically purple)?

It sounds like the encryption section has degraded and can't be read reliably.