TC timers - WAN performance testing

Love Knoppix and would like to use it as a quick implementation of NIST/DummyNet/TC-NETEM for WAN performance simulation testing. TC and NETEM are built in, which is perfect for my needs, but I have found an interesting 'bug'. If I introduce delay on the loopback or ethernet interface the timers are variable - sometimes with a great degree of variance. I do not have this issue on the same machines using TC with FC4. DummyNet on FreeSBIE is very consistent, so I presume that RAMdisk and optical media factors (not that I would think that they would be an issue) are not a concern (thinking IO DMA, etc).

Any thoughts on this one - I can use FreeBSIE, but its NIC support is not as strong and I'm happier to only use one LiveCD to make things happen. I'm a network architect for a large financial, and getting folks to use these tools is easy with a Live CD, but really tough if I use words like install and compile the kernel... :)