HTTP server devel: MSIE replies "Cannot find server or DNS Error" after larget POST request

Hi to all and thanks in advance.
Recently I've encountered a problem and searching for solution gave me
nothing =( So could you please help if you know this problem or have a
guess of possible cause.

I developed a lightweight and simple HTTP server in C++ in UNIX
environment. It meets HTTP/1.0 and couple of features found in
HTTP/1.1. It supports url-encoded posts and does not support
keep-alive. Everything works fine but the only problem:

When posting relatively big form-entry (~2kb) with MSIE it shows
"Cannot find server or DNS Error" page. Actually the post HTTP request
is performed correctly and my server is answering with valid HTTP 200
OK,
HTML is quite the same as usual. This problem doesn't appear with other

browsers (konqueror,mozilla,firefox). Personally I observed this
problem
with MSIE 6 on win2k, but reports have come from winxp with
unidentified
MSIE. I traced tcp with tcpdump -A and it looks fine for me. I tried
both
replying Content-length and not and it's all the same. And the most
strange
about it is that sometimes (quite rare) MSIE actually shows me valid
reply.

So, my questions are for HTTP server developers primarily
- is this the known issue about MSIE?
- What additional requirements could MSIE impose on web server?
- What are possible reasons of this error message?
- Anything else? :)

If this will seem helpful I can post and additional details regarding
this issue and
may be even allow public access to the server.

Thanks in advance,
Peter.

Thanks for all paid attention.
Socket shutdown and 500 millisecond delay actually solve the problem.