NWDS 7.3 some infrastructure servers cannot be contacted

Hi

When I am trying to Import the track in NWDS 7.3 I am getting the following error.

"some infrastructure servers cannot be contacted"

I am trying to Import from System Landscape Directory

and in Windows --> Preferences --> Development Infrastructure --> System Landscape Directory

When I place the URL and click on Ping

The Ping is successful

When I am trying to import a New Development Configuration by doing Import from System Landscape Directory and I can see all my tracks and everything

I can see Remote Development Configuration

But when I try to logon to Development Infrastructure it gives me the following error

"some infrastructure servers cannot be contacted"

Can some one let me know what I need to do to resolve this error.

Regards

JM