I am unable to build DVD using Encore

Hi there,
I have been working on a number of DVDs with various timelines for sometime.
Having transcoded everything in the format that I wanted, I tried to build up the DVD using Encore and got this error message.
I need someone to help me out?

PGC “Main Title” has an error at 0.6340s.
The aspect ratio of this file is not supported by DVD. – PGC
Info: name = main Title, ref = Cpgc, time = 0.6340s
I appreciate your help.
