I get an error while building up DVD using Encore

I have a request,
I have been working on a number of DVDs with varied timelines for a while now.
Having transcoded everything in the format that I wanted, I tried to build up the DVD using Encore and the below error message appeared on the screen.
Does someone know what the problem is?

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
Most grateful.
