The same thing seems to happen for both "Requested Range Not
Satisfisfied" and for "I do not accept If-Unmodified-Since" -

new.txt :
15:12:38	0/-1	-R-M--	416	error
('Requested%20Range%20Not%20Satisfiable')	text/html
date:Sat,%2001%20May%202004%2013:09:26%20GMT
images.epilogue.net/users/chrisja/Orc_Female_Lyzoria.jpg
F:/Web%20Sites/Epilogue/images.epilogue.net/users/chrisja/Orc_Female_Lyzoria.jpg
(from www.epilogue.net/cgi/database/art/view.pl?id=55971)

hts-ioinfo.txt :
[789] request for
images.epilogue.net/users/chrisja/Orc_Female_Lyzoria.jpg:
<<< GET /users/chrisja/Orc_Female_Lyzoria.jpg HTTP/1.1
<<< If-Unmodified-Since: Fri, 06 Feb 2004 20:31:46 GMT
<<< Range: bytes=190159-
<<< Referer:
<http://www.epilogue.net/cgi/database/art/view.pl?id=55971>
<<< Connection: Keep-Alive
<<< Host: images.epilogue.net
<<< User-Agent: Mozilla/4.5 (compatible; HTTrack 3.0x;
Windows 98)
<<< Accept: image/png, image/jpeg, image/pjpeg,
image/x-xbitmap, image/svg+xml, image/gif;q=0.9, */*;q=0.1
<<< Accept-Language: en, en, *
<<< Accept-Charset: iso-8859-1, iso-8859-*;q=0.9,
utf-8;q=0.66, *;q=0.33
<<< Accept-Encoding: gzip, identity;q=0.9

[789] response for
images.epilogue.net/users/chrisja/Orc_Female_Lyzoria.jpg:
code=416
>>> HTTP/1.1 416 Requested Range Not Satisfiable
>>> Date: Sat, 01 May 2004 13:09:26 GMT
>>> Connection: close
>>> Content-Range: bytes 190159--1/190159
>>> Via: 1.1 ndf-cache2 (NetCache NetApp/5.5R3D3)

new.txt :
15:12:40	63/63	-R-M--	412	error
('I%20do%20not%20accept%20If-Unmodified-Since')	text/html
date:Sat,%2001%20May%202004%2013:07:57%20GMT
images.epilogue.net/users/chrisja/The_Coldest_Day.jpg
F:/Web%20Sites/Epilogue/images.epilogue.net/users/chrisja/The_Coldest_Day.jpg
(from www.epilogue.net/cgi/database/art/view.pl?id=55959)

[791] request for
images.epilogue.net/users/chrisja/The_Coldest_Day.jpg:
<<< GET /users/chrisja/The_Coldest_Day.jpg HTTP/1.1
<<< If-Unmodified-Since: Fri, 06 Feb 2004 17:49:00 GMT
<<< Range: bytes=123453-
<<< Referer:
<http://www.epilogue.net/cgi/database/art/view.pl?id=55959>
<<< Connection: Keep-Alive
<<< Host: images.epilogue.net
<<< User-Agent: Mozilla/4.5 (compatible; HTTrack 3.0x;
Windows 98)
<<< Accept: image/png, image/jpeg, image/pjpeg,
image/x-xbitmap, image/svg+xml, image/gif;q=0.9, */*;q=0.1
<<< Accept-Language: en, en, *
<<< Accept-Charset: iso-8859-1, iso-8859-*;q=0.9,
utf-8;q=0.66, *;q=0.33
<<< Accept-Encoding: gzip, identity;q=0.9

[791] response for
images.epilogue.net/users/chrisja/The_Coldest_Day.jpg:
code=412
>>> HTTP/1.1 412 I do not accept If-Unmodified-Since
>>> Date: Sat, 01 May 2004 13:07:57 GMT
>>> Content-Length: 63
>>> Content-Type: text/html
>>> Server: publicfile
>>> Via: 1.1 ctb-cache1 (NetCache NetApp/5.5R2D6), 1.1
ndf-cache2 (NetCache NetApp/5.5R3D3)

Both files were on my hard drive before this error occurred,
they are now gone. Nothing is reported about these files in
hts-log.txt. Hehe, and I hadn't realised this was reported
so long ago! :)

Thanks
Andrew