iso or avi on dvd???

[ipod]

I have some tv series episodes on my HDD, and when the AVI's are converted into an ISO and burned to disc, some episodes won't play whereas other will. With the ISo the LG rc299h dvd recorder will recognize them as DIVX and I can get more files onto a dual layer disc, as appose to burning the AVI's. Using Ultra ISO, Img Burn, and Convert 'x' to dvd. Is there something that I am doing wrong??

Please Help.

Ipod.