errors while running lisp

[vivekgrs]

hi everybody
i had developed one lisp program. that's working fine in some drawings and in some drawings, its showing error. the errors are mention below:
1) bad argument type consp nil.An error has occured inside the * error * function autocad variable setting rejected cmdecho nil.

2) bad argument type for compare : "6" 0

can anyone guess the fault in the program by seeing errors. if so , plz suggest me to proceed.

regards
m.arunachalam

[kpblc]

Show the code please.
===
Added:

(setq _cmdecho_ (getvar "cmdecho"))
(setvar "cmdecho" 0)
;; Your code
;; at the string you setting sysvar "cmdecho" try something like this:
(if _cmdecho_ (setvar "cmdecho" _cmdecho_))