Max speed is a stat that is highly sensitive to GPS error. The raw number reported in the main TF window is the actual highest speed in the file. IIRC, the profile tool throws out the highest 2-3 speeds so that it can give a more reasonable profile. That may account for the difference.
Also, there is a setting (prefs->units) for the maximum speed allowed in the software. For instance, all my GPS data is human powered, so setting it at 50mph or so makes sense because I rarely go faster than that. A hiker/runner may set it even lower.
The GPS itself has more information available to it (e.g. # of satellites, signal strength) and may decide to not use a particular point for max speed. Unfortunately TF really can't tell whether you just went that fast or whether that point is an error and shouldn't be counted.
Hope that helps. If you can't figure it out I'd be happy to take a look at your file and tell you exactly what's going on.
