[CentOS] Kickstart issue: 'dialog' doesn't work in %post, CentOS 5.5

[John Doe]

From: Zhang Huangbin <zhbmaillistonly at gmail.com>
> I'm trying to customize a CentOS installation cd, but got 
> trouble with kickstart.
> I want to use dialog[1] for command line based 
> user interface, but it can't display correctly in kickstart with CentOS 5.5. 
> Same ks file works with CentOS 5.3 (both i386 and x86_64).

What does "can't display correctly" mean?
Checked /etc/termcap for available terminals?

JD