Version:            (using KDE KDE 3.1.4)
Installed from:    SuSE RPMs

As far as I can tell, KNode fails to properly format the reference list for any message with more than 16 references.  A message with 16 references will have the line as follows:

References: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

However, for 17, 18, 19, etc., we get the following:

References: %2 2 3 4 5 6 7 8 9 10
References: 1 %2 3 4 5 6 7 8 9 10 11
References: 1 2 %2 4 5 6 7 8 9 10 11

Clicking on this mysterious %2 reference results in an invalid article ID and, not surprisingly, an "article not found" message.  KNode seems to be mangling (i.e., truncating, and then adding junk to the end of) the actual article ID of one of the referenced messages.

An example of a post evoking this behaviour is <0b53qvo99gcbe7m3ctku9vtu5uv28k8csu@4ax.com>, though I suppose it wouldn't be hard to construct your own 17-message long thread on a local news server or in one of the *.test groups for debugging purposes.