VMware Server 1.x  has incomplete USB 1.x support and you may not be able to use some USB devices with it. You may try the same solution which is described for ESX below.

VMware Server 2.0 will have USB 2.0 support, however Server 2.0 beta releases still struggle with it.

VMware Workstation 6 has USB 2.0 support which is reported  to work quite well.

With VMware ESX you should only consider using USB on the Service Console, for example in order to transfer some file into the console. Using a USB device with a VM on ESX is not supported. A way to overcome this is to use a commercial solution for USB-over-TCP/IP. This works by installing a special USB driver installed into the guest, which accesses a LAN/USB gateway dongle. See http://www.vmware.com/pdf/esx_anywhereusb2.pdf for more information.