i have time machine backing up its done about 4 now but when i click on time machine logo in the dock the mac freezes up

i then have to do a hard restart

anyone know what could be causing this?

here is a crash report if that helps as i dont understan them

Sun Nov 11 09:55:23 2007
panic(cpu 0 caller 0x00043EA4): "zalloc: \"ipc kmsgs\" (112 elements) retry fail 3"@/SourceCache/xnu/xnu-1228/osfmk/kern/zalloc.c:770
Latest stack backtrace for cpu 0:
0x0009AD18 0x0009B6BC 0x00029DC4 0x00043EA4 0x0001B860 0x0001BE7C 0x0002C390 0x0037A92C
0x0033CE90 0x0033D104 0x0033CFF4 0x003424E8 0x00344E1C 0x00343E38 0x000AFE54
Proceeding back via exception chain:
Exception state (sv=0x6c3e0780)
PC=0x00000000; MSR=0x0000D030; DAR=0x00000000; DSISR=0x00000000; LR=0x00000000; R1=0x00000000; XCP=0x00000000 (Unknown)

BSD process name corresponding to current thread: kernel_task

Mac OS version:

Kernel version:
Darwin Kernel Version 9.0.0: Tue Oct 9 21:37:58 PDT 2007; root:xnu-1228~1/RELEASE_PPC