samba - Jul 2008 - oplock problem with teracopy (oplock_timeout_handler)

Using Samba 1:3.0.28a-3 from Debian sid with a Windows XP SP3 client.

I'm have an odd problem using the third-party copy utility teracopy. 
Although copying from a samba share works fine with the default Windows 
Explorer client, if I use teracopy, the operation frequently gets stuck, 
and I see the following sort of errors repeatedly on the server:

smbd[24922]: [2008/07/19 10:30:31, 0] 
smbd/oplock.c:oplock_timeout_handler(356)
smbd[24922]:   Oplock break failed for file [...] -- replying anyway

Any ideas? Is there some reason teracopy would provoke an oplock issue 
but regular copy would not? Any settings that I might use as a workaround?