This is a Bootcamp Win XP Pro installation on a Mac Pro. I've had no problems with audio from line out until my last reboot. line out works fine in Mac OS. Noticed some 5000 series chipset errors in the device manager, but found a thread here stating this can be ignored and shouldn't be a problem. Keep in mind, my line out WAS working until it just mysteriously quit on my today! I've tried reinstalling Realtek drivers, and also found this thread in here: http://forums.macrumors.com/showthread.php?t=388594 which offers no solution. This is apparently a popular problem, and a really serious one for anyone like me that does professional quality recordings. Plugging into the headphone jack is NOT a solution! The headphone jack does not output line level, has the wrong impedance, and can ruin my equipment. What aggravates me is that the line out jack was working. This means that there HAS to be a solution. If it worked once, it can work again. If ANYONE has a clue how to fix this, please get back to me. In the meantime, I'll be looking on my own, and promise to return with whatever solution I find, if I do in fact find one.