What's in the path between the 2 devices, stud wall, poured concrete, brick wall? Your PC should have some indication of signal strength, what is that like? Usually you get a good signal at 25' unless there is some serious signal absorption going on over the path.

Do you know that you have a good Internet connection? Plug a PC into the router and see what speed you're getting. Maybe there are issues at the router. Another possibility is to change the channel from 6 to one that no one else in the neighborhood is using.

A further possibility is that you have 2.4 GHz cordless phones and they are messing things up.

A little more info on the setup would be helpful.