As a workaround I used to delete the old $HOME/.kde/share/apps/konqsidebartng folders when upgrading machines to KDE4. Konqueror recreates this directory when next run and I believe it just holds sidebar settings as per its name - not, for example, bookmarks. As well as clearing out the old URLs it also clears out the defunct icon names.
As a workaround I used to delete the old $HOME/. kde/share/ apps/konqsideba rtng folders when upgrading machines to KDE4. Konqueror recreates this directory when next run and I believe it just holds sidebar settings as per its name - not, for example, bookmarks. As well as clearing out the old URLs it also clears out the defunct icon names.