Here's the content of an email from one of my local
Roundup users:

Looks like a typo'd when entering a superseder and it
blew up because the issue I tried to supersede from did
not exist.
Just thought you'd like to see a way that you could
blow it up.

Traceback (most recent call last):
 File
"C:\Python22\lib\site-packages\roundup\cgi\client.py",
line 764, in newItemAction
   nid = self._createnode(props)
 File
"C:\Python22\lib\site-packages\roundup\cgi\client.py",
line 1030, in _createnode
   return cl.create(**props)
 File
"C:\Python22\lib\site-packages\roundup\backends\back_anydbm.py",
line 842, in create
   raise IndexError, '%s has no node %s'%(link_class,
IndexError: issue has no node 292