OK, here's the weirdness I'm experiencing: wireless to LAN speeds seem fast, wired Internet speeds seem fast, wireless Internet speeds are slow for two Windows XP Toshiba laptops.
Other wireless laptops (Windows 7, FYI) have no problem speed testing up to the full 7-8 Megabits of Internet bandwidth but these two Toshiba laptops can never test above 3.25 Mbps or so. If I wire them directly to the router they test up to the full 7-8 Mbps. I've also tested transferring files from a server on the LAN to the laptops and I got around 14Mbps (which is acceptable for 54 Mbps wireless with encryption) so I know the wireless devices are capable of those speeds.
I've tried bypassing the on-board wireless and using a 'N' mode USB network adapter connecting at 130 Mbps and still get the slow Internet speeds.
I've tried switching between WEP and WPA as well as swapping the original 'G' mode router for an 'N' mode router and trying various channels.
I've also tried disabling all firewalls and AV on the laptops to no avail.
I'm really scratching my head on this one now after everything I've tried. Ideas?