Sometimes .htc files can't be downloaded.

[Guest_imported]

First of all, sorry for my poor English.(from Japan)
I'm using IE6, and the server's environment is IIS5.0 and
WAS(IBM WebSphere).
The pages including element behavior(=.htc) sometimes
cause "Page not found.(DNS error)", but some other time
they go well on the same environment.
Then, I took HTTP trace and analyzed it.
As the result, I found IE6 uses 2 TCP/IP ports to
download the contents(.js .css .htc etc) and somehow
the RESET(TCP) is send as response for the GET request to
.htc file.
But, when the downloading goes well, the same .htc file
is downloaded 2 times A session and at that time the
RESET is send on another port other than the port using
for downloading the .htc file.(???)
Is this phenomenon caused by my wrong environment or
settings?
I can't find any solution for this in Japan so far.
It's verry helpful to give me any advice.
Thank you.