ASUS P5KPL-AM motherboard on-board sound laggs

[C. G.]

My motherboard's integrated sound chipset works, but when I watch a film, it only works fluently when the film is in a small window. As soon I enlarge the video player's window or maximize the film, the sound laggs a lot, and the video, too. But I think the problem comes from the sound driver and not from my graphics card nor it's driver because it's an nVidia GeForce 9800GT which works perfectly and it's driver, too. I don't have this problem with the same computer on Linux or Windows, just FreeBSD.

Here is the output of my "lspci -v" command :

00:1b.0 Audio device: Intel Corporation 82801G (ICH7 Family) High Definition Audio Controller (rev 01)
    Subsystem: ASUSTeK Computer Inc. P5KPL-CM Motherboard
    Flags: bus master, fast devsel, latency 0, IRQ 16
    Memory at f9ffc000 (64-bit, non-prefetchable)
    Capabilities: [50] Power Management version 2
    Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
    Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00