JavaScript :: Embedded Flash MP3 Player Slow On Some Files

I am using a embeddable Flash based MP3 player (The standalone Version of Wordpress Audio Player, to be exact) to play audio on the web page of a client. Given the nature of Flash based players - AFAIK they all use Flash's audio/video decoding libraries - the exact player product might not matter, though. She complains that some specific audio files sometimes tend to play slowly, as if on a tape deck that doesn't run at full speed. Her machine is a 5 year old Sony Vaio with a 1.5 GhZ Pentium M Processor.

So it's not top of the line anymore but it should not have trouble decoding anything, let alone a MP3 audio stream. I can't verify the problem because we can't set up an audio connection (slow Internet on a remote island), nor can I reproduce it on my 3.3 GhZ dual-code Workstation, but this is a person whose error reports have seldom turned out unfounded in the past, so I tend to take them seriously. I see differences between the encodings of the MP3 files (see below). Any pointers towards which setting(s) to change?

This is what Winamp tells me about a file that is sometimes slow:
MPEG-1 Layer 3
128 Kbit, approx. 966 frames
48000Hz Stereo
CRC: Yes, Copyright: No

This is what Winamp tells me about a file that is never slow:
Encoder delay: 576, Zero Padding: 1584
MPEG-1 Layer 3
151 Kbit (VBR), 12405 Frames
44100Hz Joint Stereo
CRC: No, Copyright: No