PHP4/Apache2 Content-Length stripped?

Hi all, I'm writing a wap download script involving dynamic image resizing and so on. I've notice that some phones are quitting in the mids of http transfer. After looking further I found out that headers() is sometimes ignored or stripped. I've googled around and found in a perl forum that flush-ing helps but in PHP4.3.10/Apache2/Gentoo/linux2.6 it seems to not help (at least in my configuration) Is there a work-around or something... (I'm going to post same question in apache's mailiing list..) Thanks in advance