unable to secure system preference components

Hello,

I have Snow Leopard 10.6.8 running on my macbook. Recently, I came to realize that I am not able to lock or unlock any of the components under the system preferences pane. If I unlock something, the moment I leave and return back to it, it is locked! And if something is already locked, it does not unlock at all.

I do not remember installing any third party software that tinkers with the sys_pref properties.

I tried to search on google. But I couldn't find a post that had a similar problem as mine or may be I was not using appropriate search words.

Could anyone here please suggest a solution?

Many thanks