I've been struggling with this for a while now...
I have a Linksys wireless-B router (the standard $50 one from about 3 years ago). I also purchased a Linksys PCMCIA wireless card Model# WPC11 ver.3 with it. Together they work great and I get a transfer rate of 11 Mbps (my hi-speed DSL connection seems to be around 2-3 Mbps. I have a Dell Inspiron 600m laptop with its own internal wireless adapter (Dell TrueMobile 1300 WLAN Mini-PC and a new Dell Inspiron 1501 that has a built in wireless adapter (supporting 802.11n technology.
My issue with both laptops is that when I unplug the PCMCIA card and only enable the internal wireless adapter, the transfer rate drops from 11 to 1 Mbps and I can barely load any web pages. This happens even when the signal strength is Excellent and all bars are green.
Am I missing something here? It could be a configuration issue with my wireless router or perhaps old firmware, but when I use the external PCMCIA card, everything is great. Please help!