Strace couldn't trace anything for me:(

[Tian, Kevin]

Hi, all,
	I couldn't remember what I had done to my Tiger machine based on
Itanium processor. Now the strace couldn't trace any process with
following messages:
		
execve("/bin/ls", ["/bin/ls"], [/* 26 vars */]) = 0
upeek: ptrace(PTRACE_PEEKUSER, ... ): Input/output error

	However several days ago I ran strace happily :(. The strangest
issue is that 32bit strace instead worked well on IA64 machine, which
could trace 32bit apps. From the manual for strace, PTRACE_PEEKUSER is
to fetch something in user's memory. With -d option, I got:
	
execve("/bin/ls", ["/bin/ls"], [/* 26 vars */]) = 0
 [wait(0x137f) = 1090]
pid 1090 stopped, [SIGSTOP]
 [wait(0x57f) = 1090]
pid 1090 stopped, [SIGTRAP]
upeek: ptrace(PTRACE_PEEKUSER, ... ): Input/output error

	Who can tell me what happened? Even reboot couldn't correct this
fault behavior.

Many thanks,
Kevin