[CentOS] tty login hangs

Hi all,

I have two servers both identical in hardware and I have just done a
clean install of CentOS 5.2 x86_64 on both.

Sometimes (more often than not) when I log in at the physical console
(e.g. tty1, tty2, etc.) I will be logged in and it stops responding even
if the shell is not doing anything.

When this happens I can still switch to another VT with alt+f2 and login
as normal.

I don't know if bash, mingetty or whatever process is locking up. If I
do a `ps ax` all processes are sleeping.

Any idea's what could cause this?

Thanks