Understanding that my problem could have a very vast scope of possibilities, I'll accept the answer that points me to something that I might have missed.
My software's client is facing this issue of page stopping loading in the middle and that too happens randomly. As usual, this does not happen in out network even with guys doing VPN from remotest parts of the world. The page is only 14 KB.
Its a web-based software that serves HTML via Apache over HTTPS. Client is using IE8 browsers.
We did network trace and found that not only number of bytes differ from our end to the trace at client's end, even encrypted packet sequence also differ (after a while in the stream). But that happens for successful request too!
Has someone experienced similar issue? What could corrupt the stream?
PS: Client has PIX firewall just in case somebody has seen something similar.