screen lock problem

hi friends

i have a small problem,in my redhat enterprise linux system screen lock is not working
if i click screen lock no action takes place...

so is there any solution to fix this problem or any alternate method available please let me know....

waiting for replys.......

thanks & regards
madhusudan:)

need help urgently........ please anyone:(

Maybe there is something wrong with your xlock program. Open a xterm window and try the command "xlock". Does that work?