pending in logon conection to Netweaver by SAPGUI

Hi All

We have an internal system of NetWeaver 7.41.   Since its initial installation, it had been working well. However, this week, when I tried to logon to the system by SAPGUI, it is always pending on state of waiting for connection, and I saw the state of disp_work.exe as 'Yellow'. 

I attached the log dev_disp.

thanks,

Torren