If you are running a wired connection you should be OK. What are the PC specs of the PC used for serving the video? Do you have any anti-virus software on your PC?
I have 5 wired systems (3 are test systems) and results are the same.
USB Direct is no different with a 24MB/s flash drive.Network is 10/100/1000 wired, and yes, I have tried different switches.
1st- Q6600 @ 3Ghz, 8GB, 1.5TB SATA (Raid 0), 8800 Ultra and SB Xi-Fi Xtreme Fatal1ty Pro on Vista 64 (Primary)
2nd - X2 4400, 2GB, 400GB SATA (Raid 0), 7800GTX, SB Audigy on XP Pro. (Secondary)
** Test Systems **
3rd - P4 3.2Ghz, 2GB, 750GB SATA, 7800GT, SB Audigy on XP Pro (No Firewall, No A/V)
4th - P4 3.2Ghz, 2GB, 300GB SATA, Radeon X800, on-board audio on XP Pro
5th - Dual 3.2Ghz Xeon (604), 8GB, 320GB SATA (Raid 0), on-board audio on 2003 Server
Other stuff plays okay, for the most part, but these NASA videos are terrible on my DSM-520.