Error opening the wallet 'kdewallet'. please try again.

If you use the 'kdewallet' in ubuntu,sometimes maybe forget the password you have set.When you open some software ,ubuntu will prompt the error message just like 'Error opening the wallet 'kdewallet'. please try again....'.
One way to solve this ,you have to click 'cancel' button every time , the other just find the '/.kde/share/apps/kwallet/kdewallet.kwl ' file ,delete it ,or rename it as a bak. Then it will be ok.