iDirect iBuilder & iMonitor

Our iDirect's iBuilder & iMonitor software can not log on to NMS.
I can ping to NMS and all our remotes are also working well.
But the problem is I can't log on iBuilder & iMonitor suddenly.
Yesterday, I could log in successfully, there was no problem
at all.
What problem can it be ??
Is there anything should I need to check ??
It's showing only " Connecting to server. Please wait"
in iMonitor,
"Logging on" in iBuilder.
Any idea about it , please..! Thanks