Hi Manna,
Are you able to ping or telnet the system "10.1.1.20" ? If yes then if you could try adding some entries in the services file of that Windows 7 PC, I had somewhat similar issue on a Windows 7 x64 PC where I added " sapms<SID> 3601/tcp" entry in Services file ( Path: C:\Windows\System32\drivers\etc) and then it worked fine. Give a try if this works for you.
Regards,
SUJIT