My internet speed is around 10 Mbps. Pages load in less than a second. However, when I use the wireless internet, pages that normally load in a second now load 20 seconds and sometimes up to a minute. The little wireless icon in my taskbar says this:
Your connection may be 54M but the data transfer rate is much slower (11M), and is also affected by such things as signal quality, interference, security implimentation, AP mode, and obviously the quality of the equipment being used.
Do some research about external factors in your area (net stumbler is a good start).
It sure sounds like an interference issue. Expanding a bit on Fred's mention of interference. What other wireless gizmos are around you? Commonly mentioned:
Broadband speed but incredibly slow wireless 
Linear Mode
