hmmm...what if you try the default httpd.conf ? (doubt my.cnf is related to this issue)
Any additional non-standart modules for apache or php?
[EDIT]
I think I know what do you mean, I also noticed that when I open my pphlogger page which takes about 1-2 minutes to open, I can not use the same domain to browes other pages...I thought it was windows limitation of some kind...never tryed to investigate it...
But, your case is little different, because file data is being sent out to the browser, while in my case the browser waiting for server responce...
Sorry dont have an answer..