Missing User Export Presets

[Rusty]

This may or may not be connected to my recent registration of Jeffery Friedl's Zenfolio export plug in.
Yesterday on opening Lightroom 2.6 I got a different than usual message that explained to me what all the side panels were and highlighted each as I clicked through the next buttons. Lightroom appeared to be working fine until I went to export some files.
All my user presets were missing, no great loss, but the Zenfolio export preset is also gone, which is a loss.
I have reloaded LR, no changes.
Running win vista 32bit.
Suggestions please and thanks in advance

[Rusty]

Jeffery Friedl has been most helpful. The suggestion is that the prefernces files have been corrupted, I'm still working on that aspect as my user presets are gonzo.
I have dealt with the Zenfolio Plugin thanks to Jeffery.
Advice on finding missing user presets will be greatly appreciated.