Version:           4.1.00 (KDE 4.1.0) (using 4.1.00 (KDE 4.1.0), Kubuntu packages)
Compiler:          gcc
OS:                Linux (i686) release 2.6.24-19-generic

In order to prevent false positives I checked this behaviour with
- Internet Explorer 6 (wine)
- Firefox 3

Both browsers had no issue with IBM Sign In.

Problem:
Call www.ibm.com and follow the link "Sign In" at the top on the right corner.
A new window pops. Fill in your login information and submit.
Konqueror seem to process then after one minute I get this well known error page within konqueror:

The requested operation could not be completed
Unknown Host
Details of the Request:
URL: https://www-304.ibm.com/pkmslogin.form
Protocol: https
Date and Time: Monday 04 August 2008 08:16
Additional Information: www-304.ibm.com: Unknown error
Description:
An unknown host error indicates that the server with the requested name, www-304.ibm.com, could not be located on the Internet.
Possible Causes:
The name that you typed, www-304.ibm.com, may not exist: it may be incorrectly typed.
There may have been a problem with your network connection.
There may have been a problem with your network configuration. If you have been accessing the Internet with no problems recently, this is unlikely.
Possible Solutions:
Check your network connection status.
Contact your appropriate computer support system, whether the system administrator, or technical support group for further assistance.