Version:            (using Devel)
Installed from:    Compiled sources

Konqueror refuses to open an URL with an underscore. I tryed to open:
http://vzory_smluv.a4.cz/protokol.html

Konqyeror shows only a meessage box with "Malformed URL
http:/protokol.html" text and refuses to open it. Other applications - Firefox, curl, wget - opens it without a problem.

The a4.cz is accessible, but when I type vzory_smluv.a4.cz (or http://vzory_smluv.a4.cz, or http://foo_bar.com) into adress bar I got the error page

The requested operation could not be completed
Unknown Host
Details of the Request:
URL: http:
Protocol: http
Date and Time: Tuesday 29 December 2009 10:08
Additional Information: 
Description:
An unknown host error indicates that the server with the requested name, , could not be located on the Internet.
Possible Causes:
The name that you typed, , 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

and adress bar contains the "http:" only.