Sample Rate Differences?!

[GangstaRap]

I tried to save some .AVI file with new audio compression...
so i choose "Lame MP3, 48000 Hz, 128 Kbps, CBR, Stereo"
but when i try to save it - i'm gettin this massage:


OK...
so i went back to "compression", this time pickin "Lame MP3, 44100 Hz, 128 Kbps, CBR, Stereo"

this time it worked...

why does VirtualDub resist to 48000 sample rate?
does 48000 sample rate is better quality then 44100?

Thanks in Advanced!!!

[Alex_ander]

This means the original audio in video file has 44.1 sample rate and the mpeg encoder doesn't perform resampling to another value.
There's no quality gain with going 44.1 => 48, it is only done if one wants to make the audio DVD compatible. Original sampling at 48 is a bit better since it allows for keeping wider audio frequency range (up to 24kHz theoretically).