On my gutsy box, I use Cisco's vpnclient-linux-x86_64- to connect to my work, but the upload speed is near zero when connected. I'm lost to determine where the bottleneck is. Can anyone point me to some tools I can use to determine why it's so slow?

Before someone suggests using vpnc instead - I can't. We use HMAC-SHA authentication, which isn't supported by vpnc.