stuck at ubuntu server login loop

Today I downloaded and installed xshell 6 in my window 7 computer and use mysecureshell for my ubuntu server. I initially tried to connect to my ubuntu server from my Windows 7 computer using SSH protocol and that works fine. After that, I tried to connect to my ubuntu server from my Windows 7 computer using SFTP protocol and that works fine too. However, after ending the SFTP session and tried to connect to my ubuntu server again using SSH protocol, the connection failed. I then exit from the Xshell program and restart my ubuntu server, but now I neither could login to my Ubuntu server nor access the Ubuntu server from my PC using SSH protocol but I still could access the Ubuntu server using SFTP protocol. I just keep getting login loop when I enter my username and password correctly.
What could go wrong to my Ubuntu server? Could using the SFTP protocol interfere with something in my Ubuntu server? Attached is the screen shot from my ubuntu server after start up and just before login.

Thanks a lot for any suggestion that could sort my problem.

Program Ver. : Xshell 6