Add IPs on ethernet and removed

I have facing a difficult problem, I had configured OpenVPN on windows 2008 server R2 which is configured with TUN mode and assigning public IP's to clients,

Problem is that no internet active on clients end, but when I put some IP's on windows ethernet connection and remove these IP's after few seconds, internet become active for the client, anyone have at idea about it.

Regards,

Jebran.