USB-UIRT problems w/ high CPU utilization

I just received my USB-UIRT yesterday. I'm using it with Girder to control ZoomPlayer and myHTPC.
It works great w/ myHTPC and to control ZoomPlayer to play back XVID movies on my 2.4GHz P4 Shuttle SB61G2. But...
When I start playing a wmv file in ZoomPlayer encoded at 640x480 30fps encoded in WMV9 (Windows Media Video 9), I'm unable to reliably get IR codes through to ZoomPlayer.
I've tried different remotes, substituted Windows Media Player for ZoomPlayer, and re-updated the firmware (5.4) and Girder plug-in (2.5.9) to no avail. The light blinks, but the code is only received maybe 5% of the time.
I think I've isolated the problem down to high CPU utilization. Playing back the XVID, my CPU utilization is about 10-12%. Playing back the WMV9, it's on the order of 35-40% (this is on a P4 2.4 800MHz FSB w/ Hyperthreading enabled).
I tried bumping the priority of Girder to Realtime, which didn't help (I'm running Windows XPSP1).
My understanding is that USB-UIRT doesn't use the system CPU to decode the IR, so I'm a little confused at this point. Does it poll the USB device to receive the codes, and could it possibly be missing a polling opportunity since the CPU is busy decoding video?
Thanks in advance for any help or solutions people can provide.
It works great w/ myHTPC and to control ZoomPlayer to play back XVID movies on my 2.4GHz P4 Shuttle SB61G2. But...
When I start playing a wmv file in ZoomPlayer encoded at 640x480 30fps encoded in WMV9 (Windows Media Video 9), I'm unable to reliably get IR codes through to ZoomPlayer.
I've tried different remotes, substituted Windows Media Player for ZoomPlayer, and re-updated the firmware (5.4) and Girder plug-in (2.5.9) to no avail. The light blinks, but the code is only received maybe 5% of the time.
I think I've isolated the problem down to high CPU utilization. Playing back the XVID, my CPU utilization is about 10-12%. Playing back the WMV9, it's on the order of 35-40% (this is on a P4 2.4 800MHz FSB w/ Hyperthreading enabled).
I tried bumping the priority of Girder to Realtime, which didn't help (I'm running Windows XPSP1).
My understanding is that USB-UIRT doesn't use the system CPU to decode the IR, so I'm a little confused at this point. Does it poll the USB device to receive the codes, and could it possibly be missing a polling opportunity since the CPU is busy decoding video?
Thanks in advance for any help or solutions people can provide.