3Gp video not working in Samsung S3310 ?

I have just upload some 3Gp video in my Samsung S3310 but only two files are not working even the phone not showing that 3Gp file but the other video of the same format are working properly. So, can anyone tell me that what could be the problem with those 2 files ?

Those files are not properly converted or encoded in 3GP. Even if they can be played in computer, they are not in proper 3GP format suitable for your phone.