This is not an anydvd problem.
Such a question should be addressed in another more suitable forum. Please search these forums to find a more suitable forum in future.
Your problem is almost certainly disk related. The fact is that a lot of brand name companies shop around the disk manufacturers and simply label them with thier own brand. You cannot guarantee getting disk from the same manufacturer each time.
There is a good piece of freeware DVD Identifier (search the web) that helps you identify the manufacturer.
In the mean time, simply try another brand e.g. Verbatim, Sony etc.