If you have an ethernet card in the momdem then you should use that instead of the usb -> ethernet adaptor.
Are you using winXP? if it is 98 or me check the system resources (right click my computer, properties, performance)
ideally you want 85% or higher
if it is lower than this, check out
www.sysinfo.org/startuplist and have a look at start-> run-> msconfig and see what is running that you can end
oh... and welcome to the site
