I have the same problem as the original reporter on a default Kubuntu 8.04 Beta, i386
the computer is a Toshiba A210-1BH with a Mobility Radeon HD 2400
i'm using all the current packages in hardy, and using fglrx from ubuntu repo.

on logoff, or even on Ctrl+Alt+Backspace, the system freezes. Up to this morning, i could use the SysRQ keys, but today (after some package updates), the freeze is total, caps lock blinking and strange squares blinking on the screen.

using ati opensource driver closes the problem... but that's not a solution :-)

i tested the above atieventsd.sh patch, but it was not a solution for this problem

Syslog does not give anything special : this is the log from my last session (had to reboot using power button).

Mar 31 23:24:41 portjm kernel: [  634.840659] [fglrx] Maximum main memory to use for locked dma buffers: 1898 MBytes.
Mar 31 23:24:41 portjm kernel: [  634.840694] [fglrx] ASYNCIO init succeed!
Mar 31 23:24:41 portjm kernel: [  634.841019] [fglrx] PAT is enabled successfully!
Mar 31 23:24:41 portjm kernel: [  634.841039] [fglrx] module loaded - fglrx 8.47.3 [Feb 25 2008] on minor 0
Mar 31 23:24:54 portjm kdm[15206]: StartServerSucces
Mar 31 23:24:55 portjm kernel: [  640.689353] ACPI: PCI Interrupt 0000:01:00.0[A] -> GSI 18 (level, low) -> IRQ 17
Mar 31 23:24:57 portjm kernel: [  642.596704] [fglrx] Reserve Block - 0 offset =  0X7ffb000 length = 0X5000
Mar 31 23:24:57 portjm kernel: [  642.596713] [fglrx] Reserve Block - 1 offset =  0X0 length = 0X1000000
Mar 31 23:24:57 portjm kernel: [  642.596718] [fglrx] Reserve Block - 2 offset =  0X7f7a000 length = 0X80000
Mar 31 23:24:57 portjm kernel: [  643.033771] [fglrx] interrupt source 10000000 successfully enabled
Mar 31 23:24:57 portjm kernel: [  643.033779] [fglrx] enable ID = 0x00000006
Mar 31 23:24:57 portjm kernel: [  643.033790] [fglrx] Receive enable interrupt message with irqEnableMask: 10000000
Mar 31 23:24:57 portjm kernel: [  643.048940] [fglrx] interrupt source 60000001 successfully enabled
Mar 31 23:24:57 portjm kernel: [  643.048947] [fglrx] enable ID = 0x00000007
Mar 31 23:24:57 portjm kernel: [  643.048954] [fglrx] Receive enable interrupt message with irqEnableMask: 60000001
Mar 31 23:24:57 portjm kernel: [  643.049024] [fglrx] interrupt source 00000040 successfully enabled
Mar 31 23:24:57 portjm kernel: [  643.049027] [fglrx] enable ID = 0x00000008
Mar 31 23:24:57 portjm kernel: [  643.049031] [fglrx] Receive enable interrupt message with irqEnableMask: 00000040
Mar 31 23:24:57 portjm kernel: [  643.052997] [fglrx] interrupt source ff00002c successfully enabled
Mar 31 23:24:57 portjm kernel: [  643.053001] [fglrx] enable ID = 0x00000009
Mar 31 23:24:57 portjm kernel: [  643.053006] [fglrx] Receive enable interrupt message with irqEnableMask: ff00002c
Mar 31 23:24:57 portjm kernel: [  643.053062] [fglrx] interrupt source ff00002d successfully enabled
Mar 31 23:24:57 portjm kernel: [  643.053065] [fglrx] enable ID = 0x0000000A
Mar 31 23:24:57 portjm kernel: [  643.053069] [fglrx] Receive enable interrupt message with irqEnableMask: ff00002d
Mar 31 23:24:57 portjm kernel: [  643.053119] [fglrx] interrupt source 20000400 successfully enabled
Mar 31 23:24:57 portjm kernel: [  643.053123] [fglrx] enable ID = 0x0000000B
Mar 31 23:24:57 portjm kernel: [  643.053126] [fglrx] Receive enable interrupt message with irqEnableMask: 20000400
Mar 31 23:25:39 portjm scim-bridge: Cleanup, done. Exitting...
Mar 31 23:25:55 portjm console-kit-daemon[6348]: WARNING: Unable to activate console: No such device or address
Mar 31 23:26:52 portjm syslogd 1.5.0#1ubuntu1: restart.

Thanks

JMB