xwinclip consistently unable to open clipboard

[Ed Avis]

Because of experiencing hangs when using the built-in clipboard
support (see other threads), I have switched to running xwinclip.exe
separately.  It normally works but recently, with the X server having
been running for a while, xwinclip died with 'unable to open
clipboard'.  The full output was

UnicodeSupport - Windows NT/2000/XP
Unicode clipboard I/O
SelectionNotify - Reasserted ownership of ATOM: PRIMARY
[above line repeated many times]
OpenClipboard () failed: 00000000

Previously, I've had xwinclip crash but been able to restart it.  But
now when I try to restart xwinclip it dies immediately:

UnicodeSupport - Windows NT/2000/XP
Unicode clipboard I/O
OpenClipboard () failed: 00000000

Hmm, I was going to say, this happens every time I run it.  But during
the course of writing this message I pasted some text from the command
prompt window into PuTTY, and that seems to have cured the problem -
xwinclip is now chugging away happily.

So I just mention this in case it is interesting - sorry that I can't
reproduce the problem every time.  I am running XFree86-xserv 4.3.0-44
and XFree86-xwinclip 4.3.0-2.

-- 
Ed Avis <ed@membled.com>