If you execute a find() that fails on the server, then a statement with a JS parsing error on the client, the shell prints the previous server error a second time:

> db.foo.find({$where:"x"})
error: {
"$err" : "error on invocation of $where function:
JS Error: ReferenceError: x is not defined nofile_a:0"
}

> db.foo.find({$where})
Tue Mar 30 11:34:04 JS Error: SyntaxError: missing : after property id (shell):0
error on invocation of $where function:
JS Error: ReferenceError: x is not defined nofile_a:0