I'm seeing the same thing on Vista64 on a clean install of flexbuilder, specifically the Flex Build Path is blank, and the ant build properties dialog is blank.
You are probably running Logitech SetPoint. Try killing all setpoint processes. (you don't even have to restart flex). It worked for me :-S
this is happening when you run flex builder on 64bit operating system. i have the same issue.
I had the issue with Window7 x64 Ultimate with FB3 Pro and shutting down Set Point seems to have fixed the issue.
According to this Adobe forums post, there are multiple causes:
SetPoint (as indicated by Scheea)
Wacom Tablet drivers
In addition, comments suggest the following:
- UltraMon
These seem to suggest that the cause is any program which monitors keystrokes or mouse movement.
Workaround: In the new wizard dialog above, note the question mark on the bottom left (the help button). When you click on the help button a help panel is added to the dialog on the right separated from the main dialog by a splitter. When you drag the splitter the rest of the dialog appears. You may need to scroll to a position where you can see all of its contents, but it should become usable. Resizing the dialog alone was not sufficient for me.
In addition, I couldn't fully use the mouse to select elements so I had to type into the filter field in order for the correct projects to show up.