Version:           1.2.5 (using KDE KDE 3.5.5)
Installed from:    Compiled From Sources
Compiler:          gcc (GCC) 3.3.5 (Debian 1:3.3.5-13) n/a
OS:                Linux

Receive a feed w/an invalid link.  Click on the link and let akregator open it, after getting the 404 click reload inside the 404 canvas and boom.

Here's some debug output.

#5  0xb77f6831 in KHTMLPart::slotFinished ()
   from /usr/local/kde/lib/libkhtml.so.4
#6  0xb7818b17 in KHTMLPart::qt_invoke () from /usr/local/kde/lib/libkhtml.so.4
#7  0xb5fad53b in Akregator::Viewer::qt_invoke ()
   from /usr/local/kde/lib/kde3/libakregatorpart.so
#8  0xb5fbd813 in Akregator::PageViewer::qt_invoke ()
   from /usr/local/kde/lib/kde3/libakregatorpart.so
#9  0xb66e79c6 in QObject::activate_signal ()
...
(gdb) x/16i $pc -16
0xb77ec821 <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+321>:       (bad)
0xb77ec822 <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+322>:
    decl   0xc9317441(%ebx)
0xb77ec828 <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+328>:       mov    (%eax),%edx
0xb77ec82a <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+330>:       test   %edx,%edx
0xb77ec82c <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+332>:
    je     0xb77ec831 <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+337>
0xb77ec82e <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+334>:
    mov    0x2c(%edx),%ecx
0xb77ec831 <_ZN9KHTMLPart12slotFinishedEPN3KIO3JobE+337>:
    mov    0x28(%ecx),%edx <== CRASH

(gdb) i reg ecx
ecx            0x0      0