SignIn.aspx?ReturnUrl=%2fdefault.aspx does not login in Windows 7

Hello,

When I try to go to my webportal, by entering user name and password and clicking login, the browser refreshes the webpage and does not log me in. However it does recognise the incorrect password. Following is the link:

SignIn.aspx?ReturnUrl=%2fdefault.aspx

Please advise.

Thanks in advance.