well, describe the symptoms, post the software (kernel, gcc, glbc) versions, hardware, io scheduler used, kernel config. The usual.
I have solved hang ups with:
echo 1500 > /proc/sys/vm/dirty_writeback_centisecs
sure, a big copy still can make other disk accesses a bit slow, but I while I am typing, I am copying a 4.4gb big iso from one partition to another... without hangs.