Disappearing up & down arrows
I have the same problem (certainly very similar symptoms).
(CS4, WinXP SP3, DataAssist 2.0.6)
If I go straight through the wizard, just changing the presentation (i.e. Style, font-family etc.), then the wizard completes, and creates the files.
But if I change labels or move columns up or down, then that's when the problem occurs.
The last two times, all's been fine until step 8, then three columns were selected at once and the up/down arrows disappeared.
After several minutes the Wizard window regained focus, and the buttons came back (briefly), enabling to move one field; then it froze again. Is it just running verrrrrry slowly? I can still select fields, it's just that the up and down arrows have disappeared. If I click Back or Next, then I have the same symptoms as the OP (i.e. an almost blank "page"), and the wizard has effectively crashed.
I've deleted the wincache file in Configuration (while DW is closed) before each error, but to no avail.
Look forward to some help. Thanks!