why gtk_label_set_text fail to change text?

["chen.shengqi" <chen shengqi connet com tw>]

Dear sirs:
    I place some GtkLabel on statusbar, and want to change the text when app is runing. but it seems that 
gtk_label_set_text sometimes will fail.
example, I set it to "kf_rpt" first, then gtk_label_set_text(..,"test1") , it show out "test1t", it seems 
tnah it copy "test1" to the text, but not release the old one. why so? how can I overcome this? 
    thanks.