Yes, I've seen this behavior as well. Its behavior is actually isolated to the Finder, not the AFP Client Core or the AFP Server process. (Attempt the same copy via ditto or cp in the Terminal and you should have no error.)
I first noticed this bug in Mac OS X 10.4.2:
http://discussions.apple.com/thread.jspa?messageID=647624
Since then, I've found that it is much less likely to happen if the server was set up with Mac OS X 10.4.3 or later
at the time when it was promoted to an Open Directory master. This means that if you used the Setup Assistant to create your Open Directory master, you may have to destroy and recreate it once you've updated your server.
I have seen the problem persist into Mac OS X Server 10.4.5 and Mac OS X 10.4.5 with Security Update 2006-002 installed. However, in that situation, the server and clients were originally loaded with Mac OS X 10.4.2 or earlier, then updated (either via Combo or multiple Delta updates over time).
--Gerrit