- I went into my Eclipse installation details and uninstalled SVNKit.
- I updated Eclipse (4.4.1RC1) and all available plugins (e.g. ADT 23.0.3). This time it was successful.
- I installed new software directly from the Subclipse site. It showed that both SVNKit and SVNKit Client Adapter were available, so I installed them. This worked fine, except that Eclipse crashed when restarting. Manually restarting after that worked.
- I updated software and a new version of SVNKit 1.8.6 suddenly was available. I installed it.