You'll know if the DVD was authored with the wrong block size as each of the VOB files will be 953 MB as opposed to the correct 0.99 GB. If it plays fine, then don't worry about it. But if the disc doesn't play, this is a likely cause.
For those of you using DVD-Lab Pro to create your titles, the patches are available that fix this problem. Fortunately for those of you who have DVDs with the 953-sized VOBS, the data can be reauthored on your computer with any number of reauthoring tools. The latest versions of Pinnacle and Nero will do this. I'll spare the details unless there is a demand for that info.