With the symptoms that you describe this usually means that either the ISO or media is bad or of low quality.
Also the burn speed may be set too high.
I've tried with different DVDs and with different ISOs (I checked the MD5), but I have the same problem everytime
If the md5sum checks out correctly, the ISO is most likely ok.
Try using the very slowest burn speed available.
Try burning the media on a different burner hardware or PC.
Try a higher quality media, such as Verbatim or such, using cd-r
, not any -rw
Hope this helps....