Uplading file via Lighttpd - system hangs

[Yury Michurin]

Hello,

When trying uploading a file to a PHP script over lighttpd, the system just
hangs.
no output to the console, no panic, just hangs.

I can still enter username/password to the login prompt from the keyboard,
but then nothing happens.
top that was running just freezes and stop refreshing.

If i change
#server.network-backend = "freebsd-sendfile"
server.network-backend = "write"

(Seen it here: http://trac.lighttpd.net/trac/ticket/1602 )
everything seems to be ok...

How can I debug that issue further?
I have no crash dump, nothing at the logs.

I've got at the kernel:
options     KDB
options     DDB
options     INVARIANTS
options     INVARIANT_SUPPORT
options     WITNESS
options     WITNESS_SKIPSPIN


I'm currently running:
FreeBSD sigma 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #7: Sat Sep 20 17:43:02
IDT 2008     yury at sigma:/usr/obj/usr/src/sys/sigma  i386
lighttpd-1.4.19_2


thanks in advance,

Yury.