ddcprobe and XFree86

ddcprobe and XFree86 report different refresh rates for the VESA modes on my PC.
Is anybody else seeing this on KNOPPIX 3.4?

I'm using a TFT display connected to a Radeon 9200, it isn't capable
of anything above 75Hz.

sudo ddcprobe
...
Established timings:
720x400 @ 70 Hz (VGA 640x400, IBM)
640x480 @ 75 Hz (VESA)
800x600 @ 60 Hz (VESA)
1024x768 @ 87 Hz Interlaced (8514A)
...

less /var/log/XFree86.0.log
...
Supported VESA Video Modes:
720x400@70Hz
640x480@60Hz
800x600@60Hz
1024x768@60Hz
...