SSL Green bar is disappearing from URL

 
Hi
In our site we are having a peculiar problem with SSL green bar.  
When we load the page SSL Green bar is showing up in the URL as usual but it diseappears after one second.
I checked the view source and all the images are pointing to https only.
I could't understand exactly what is causing the disappearing of Green SSL bar from the URL.
Is there any thing that I need to check?
Any help will be highly appreciated.
 
Thanks in advance
 
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