upgrade tool crashed (Kubuntu 7.04 to 7.10)

[peat]

Binary package hint: update-manager

After downloading all packages the upgrader crashes at installing packages.It shows the following Errormessages:

Traceback (most recent call last):
  File "/tmp/kde-root/adept_managervBmFVb.tmp-extract/dist-upgrade.py", line 59, in <module>
    app.run()
  File "/tmp/kde-root/adept_managervBmFVb.tmp-extract/DistUpgradeControler.py", line 1346, in run
    self.fullUpgrade()
  File "/tmp/kde-root/adept_managervBmFVb.tmp-extract/DistUpgradeControler.py", line 1328, in fullUpgrade
    if not self.doDistUpgrade():
  File "/tmp/kde-root/adept_managervBmFVb.tmp-extract/DistUpgradeControler.py", line 798, in doDistUpgrade
    res = self.cache.commit(fprogress,iprogress)
  File "/tmp/kde-root/adept_managervBmFVb.tmp-extract/DistUpgradeCache.py", line 69, in commit
    apt.Cache.commit(self, fprogress, iprogress)
  File "/usr/lib/python2.5/site-packages/apt/cache.py", line 203, in commit
    res = self.installArchives(pm, installProgress)
  File "/usr/lib/python2.5/site-packages/apt/cache.py", line 178, in installArchives
    res = installProgress.run(pm)
  File "/usr/lib/python2.5/site-packages/apt/progress.py", line 213, in run
    pid = self.fork()
  File "/tmp/kde-root/adept_managervBmFVb.tmp-extract/DistUpgradeViewKDE.py", line 244, in fork
    self.child_pid = os.fork()
OSError: [Errno 12] Cannot allocate memory