Knoppix 5.3.1 freezes.

I have been trying to use the live dvd for Knoppix 5.3.1.
It boots ok, with Konqueror displayed with Knoppix information. I can then
select the English version and get the info in Konqueror.
If I then try and do anything else, clicking any of the buttons along the
task bar then the system freezes. The mouse moves but pressing mouse buttons
has no affect.
Until the mouse freezes I have a full graphical environment with 'wobbly windows'
and all.
I tried booting into text mode using knoppix 2 and then X -configure. As suggested,
I then tried X -cofig //xorg.conf.new
This lead to a grey 'cross hatched' screen with a black X shaped cursor and didnt get
any further. StartX fired up X and again I had the freezing problem.
I cannot do lspci -v or any diagnostics.
I have had this problem also with Ubuntu, Linux Mint, Redhat Fedora 9.
I dont have this problem with SUSE or PCLinxOS.
Has anyone any ideas ?
System
Athlon XP 2800+
MSI KT6V-LSR (MS-7021) mobo
2Gb SDRAM
Radeon 9600 XT 256Mb RAM
master hdd Maxtor 6Y080P0 80Gb 48.5 Gb free
slave hdd Maxtor 7L250R0 250 Gb 138Gb free

This very well may not be the issue, but it would be silly to do a lot of work on this and not do the folowing test:

• Boot the Knoppix disc.
  
  At the boot prompt, type memtest and hit enter.
  
  Let memtest86 run at least 2 full passes and see if it finds any memory problems.

Memory is brand new, bought less than a week ago.
Tried Memtest as suggested, no problems.
I am not all that bothered about the freezing since I have now
settled on PCLinuxOS, but it would be nice to know what causes
the freezing in these distros and not others, if only to satisfy my
own curiosity.