I click Tool>Displacement>Create DispMap and then zbrush loads for awhile, and then creates a new alpha. But that alpha is ALL grey, why is that?
I mean, i can’t see any deformation on it… 
Have you forgotten to go to level 1 prior to creating the map? The map will be based on the differences between the current level and the highest level. If you create the map at the highest level, there are no differences and so your map turns out completely grey.
Also, don’t forget to restore your original base mesh at level one before creating the map. For more information about this, see the displacement mapping tutorials in the Help system or in the ZBrush 2 Practical Guide.
for me sometimes they appear that way so I just go to the alpha menu and reload it then viola you can see it. or I will use the crop and fill option in the alpha menu to fill my canvas with it to take a look at it and make sure all is well…but I clone it first before I do that.
did you actually texture up you model so there is something for zb to work with? did you store a morph target before beginning and restore that before creating it? if not that way did you reload the original untouched model in level one before creating the DM?
that’s all i can think of at the moment.
Let me show you…
Here im looking at the disp map in the alpha window (all grey)
If i save it as a BMP and open it in MS Paint, then it looks like this too…
Attachments
well I am no expert but some questions that may help ya somehow… how did you uv this fella? I am wondering why from the first pic that there is such a huge empty space and it seems your textured parts wrap from the bottom to the top.
also its hard to tell from the ps pic because the scroll bar is hidden from view …but that pic is at 67% and I can’t tell for sure if you scrolled down to where your displacement parts are to see if they show up in ps.
how does it look in the alpha window if you turn on max in the alpha menu? does it look the same way…i mean displacements at the bottom.