SVNKit 1.7.6 introduced couple fixes that were affecting FishEye users:

• http://issues.tmatesoft.com/issue/SVNKIT-319 Too many svnserve processes in case of svn+ssh connection
  When FishEye tries to index svn repositories over svn+ssh protocol, it creates far too many Java threads inside FishEye JVM and also spawns the same amount of svnserve processes on the subversion repository server.
• http://issues.tmatesoft.com/issue/SVNKIT-316 Diff always displays absolute paths instead of relative on Windows (even URL-URL diff)

Fisheye in 2.7.x releases use SVNKit 1.3.3, and Fisheye 2.8.x releases use SVNKit 1.7.4.

Workaround

Switch to Native Subversion Client with the latest SVNKit version (1.7.6+).