[nazim12]

It has to work 100%.
It may be you have clutter in you thumbs and/or library. (Also, be sure to have the exact same names as in the advancedsettings file).
If everything is compliant and it still does not work, then I recommend a fresh library: erase thumbs and libraries and re-scan all your media.

I hope this resolves your issues...

Can I have two advancesettings.xml because I need to increase buffer size using advancesettings.xml 

No, you can't. Only one instance is allowed. Just insert the instructions at the end of the file, after <alwaysontop>yes</alwaysontop>
Like follows:
<alwaysontop>yes</alwaysontop>
<cache>
   ....
   ....
</cache>

Thanks Resolved.