CPU has gone into STOP

We have project in PCS7 6.1 SP1 with 417-4H CPU's. Firmware V 4.0.4. System runs for about a year. Today one of the CPU's in H-system stopped for unknown reason. Diagnostic buffer contains the following messages.
The first was:

Event 58 of 3000: Event ID 16# 7301
Loss of redundancy (2oo2) due to CPU failure
CPU affected: Standby CPU in rack 1
Requested OB: CPU redundancy error OB (OB72)
Priority class: 28
Incoming event
06:06:00:304 am 02/26/08

Then

Event 57 of 3000: Event ID 16# 43E3
Master CPU: Change from redundant mode to solo mode
Previous operating mode: RUN (redundant mode)
Requested operating mode: RUN
Event occurred in the master CPU in rack 0
Incoming event
06:06:00:304 am 02/26/08

Event 56 of 3000: Event ID 16# 3502
OB request error
No relevance for user (Z1): 0000
Cause: Cyclic interrupt clock pulse generator 9
Causing OB: Cyclic interrupt OB (OB 38)
Causing priority class: 15
Requested OB: Timing error OB (OB80)
Priority class: 26
Internal error, Incoming event
06:06:00:304 am 02/26/08

Event 55 of 3000: Event ID 16# 43DA
STOP due to synchronization error between H CPUs
Previous operating mode: RUN (redundant mode)
Requested operating mode: STOP (internal)
Event occurred in the standby CPU in rack 1
Incoming event
06:06:00:304 am 02/26/08

and then some more messages about "Cyclic interrupt clock pulse generator 9".

After this CPU was started manually and H-system returned into redundant mode.
What is the failure in msg 58? and what does "Cyclic interrupt clock pulse generator 9" mean?

Dear Colleagues, I have the same problem and we Update the firmware but still have the problem.
What could be the problem?
How I couldsolve this problem?

Thank you in advance for your support.

LMA.

Hi

In that case , need to increase the scan cycle time.........