I believe I may have a solution for you in regard to the "random" KDE freezes. I also experienced the same thing going from slack 9.1 to 10. What would happen in my case was that after starting KDE and using it for 15 - 20 minutes, the mouse/desktop would freeze for 2-3 seconds, respond for a second, freeze for like 3-4 more seconds, and then be completely fine from that point on.
Now, I don't use GDM or KDM, so when I leave KDE, I exit to the terminal and I can see all the X-related messages/errors that were going on just prior to my exiting KDE. When the random freeze would happen, I quickly exited KDE to see if I could catch an error.
Prior to my coming up with this idea, I had noticed upon leaving KDE, that I would see messages regarding KDE searching for a CD-ROM drive that it had permision to access. What this had to do with was the "music CD browser" applet in konqueror. How this applet is supposed to work is to search the cd-rom for a cd and if it is a music cd, display the cd contents as folders with wavs, mp3s, oggs, etc.
In the case of slack 10, the permissions are set too restrictive for this applet to work out of the box, so the icon in Konqueror just spins and spins and spins. This is because KDE can't find a way to interface with the device specified and it starts searching through the entire contents of /dev trying to find a cdrom it has permission to open. (please note that I am using the 2.4.26 kernel - /dev is different with 2.6)
This is where the freezing part comes in. Once KDE has searched all possible devices and failed, it does something else - essentially giving up the search. I don't know what it is exactly, but it makes the system temporarily freeze as described above. Exiting from KDE to the terminal shows error messages that confirm this and KDE has now stopped searching for a cdrom. It evidently takes 15 kinutes or so for it to search through /dev.
To fix this, I needed to change the permissions of a file in /dev called sg0 or sg1, sorry I'm at work at the moment. This fixed both the applet and the freezes.
One way to tell if this is your problem is to run KDE as root with a music CD in the drive. The applet should work displaying ogg and mp3 and wav folders in the side panel. Do the same as a user and if the applet doesn't work, this could be the problem.
Sorry for the long post. If it helps you I guess it was worth it - if not , never mind
I'll check my box when I get home and edit this post to correct any errors.
Oh, and this has nothing to do with ATI drivers so thats likely something else - I use nvidia.
Indeed, the two files I changed permissions for were /dev/sg0 and /dev/sg1.
I have a cdrom and a cdburner listed as sr0 and sr1 in fstab as I use ide-scsi for both drives. These files were root:root 600 originally. I chmod 666 both files as root. Their current permissions are listed below. These are character devices. I knew to edit these because KDE told me it couldn't access them when I tried to open the cdrom as a file through konq.
steve@peggy-o:~$ ls -l /dev/sg*
crw-rw-rw- 1 root root 21, 0 1999-04-13 00:24 /dev/sg0
crw-rw-rw- 1 root root 21, 1 1999-04-13 00:24 /dev/sg1
crw------- 1 root root 21, 10 1999-04-13 00:24 /dev/sg10
crw------- 1 root root 21, 11 1999-04-13 00:24 /dev/sg11
crw------- 1 root root 21, 12 1999-04-13 00:24 /dev/sg12
crw------- 1 root root 21, 13 1999-04-13 00:24 /dev/sg13
crw------- 1 root root 21, 14 1999-04-13 00:24 /dev/sg14
crw------- 1 root root 21, 15 1999-04-13 00:24 /dev/sg15
crw------- 1 root root 21, 16 1999-04-13 00:24 /dev/sg16
YMMV - good luck