leave your display settings where they should be. your screen went blank because it does not support 1080p. only check the resolutions that will work for your tv. you do not have to do anything special or different to play a dvd.How do ya play normal dvds on the ps3 using the hdmi cable?
You can change the settings only if your tv is capable of 1080p display, but this is not required for DVD playback.
If your PS3 is connected via HDMI and it plays the games, it should play DVDs too. They both use the same drive.
Place the DVD in the ps3. GO to video on XMB, and bam...