How are you setting it up? Like uplinking from the router to the switch and everything connected to the switch? Look for collisions on the switch and router, I'm suspecting a bad port is causing the problem.
Have a 100Mbps Hub connected to a linksys router myself. I was able to get 300-500k/s upload speed before my ISP capped my upstream
So definitely you shouldn't have any problem when you're using the switch/router combo.