Current spec file defines Source0 as:

http://dl.sf.net/%{name}/%{name}-%{version}.tar.gz

which expands to:

http://dl.sf.net/clamtk/clamtk-4.45.tar.gz

which does not exist on the server:

$ LANG=en wget http://dl.sf.net/clamtk/clamtk-4.45.tar.gz
--2013-07-16 08:13:57--  http://dl.sf.net/clamtk/clamtk-4.45.tar.gz
Resolving dl.sf.net (dl.sf.net)... 216.34.181.138
Connecting to dl.sf.net (dl.sf.net)|216.34.181.138|:80... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://sourceforge.net/downloads/clamtk/clamtk-4.45.tar.gz [following]
--2013-07-16 08:13:57--  http://sourceforge.net/downloads/clamtk/clamtk-4.45.tar.gz
Resolving sourceforge.net (sourceforge.net)... 216.34.181.60
Connecting to sourceforge.net (sourceforge.net)|216.34.181.60|:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://sourceforge.net/projects/clamtk/files/clamtk-4.45.tar [following]
--2013-07-16 08:13:58--  http://sourceforge.net/projects/clamtk/files/clamtk-4.45.tar
Connecting to sourceforge.net (sourceforge.net)|216.34.181.60|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2013-07-16 08:13:59 ERROR 404: Not Found.

Please update the Source0 URL.