lisp problem for start-process

hi,
my environment ubuntu 9.10 + emacs22-nox
I've try using start-process but always got Wrong type argument:...
(start-process "my-process" "foo" "ls" "-l" "/bin/grep")
----message bar show
Wrong type argument: sequencep, #<process my-process>
----output is correct and working
-rwxr-xr-x 1 root root 100312 2009-04-28 19:03 /bin/grep
Process my-process finished
-----

how to fix Wrong type argument for this case

Thanks

This seems to be something with a return value. How do you invoke the function? For me, using eval-expression in Emacs 23.1.1 the message bar just prints the process object.

I got the solution
==wrong brace for interactive cause the problem
(interactive
(start-process ....)
)

==now without problem correct in this way
(interactive)
(start-process ....)