It's possible the files are simply not compatible with the phone. Certain java builds require specific files to work.

Hey everyone!
well, i have a problem with my t-mobile samsung SGH-t749,
ive downloaded one jad file and then a jar one to my desktop pc, then moved these two files to my phone memory card. when i took out the phone from the pc and tried to install the games manually, i got a "unsupported file type" error, and couldn install the apps, ive turned off and turned on the phone but the problem keeps on.
what can i do ? all files are in 240x400 resolution.
ive had only downloaded GuitarRockTour2.jad, and brain challenge 2 antistress.jar

thanks at all!