Slow boot time (On different places)

Ok, I think I've got an interesting case here. Whenever I use my laptop at home or at work (where my wireless connection is known and available) my boot time is regular (I'm not talking about time, I'm talking about the fact that after the desktop appears, I just have to wait round 15 seconds for the Messenger window to pop up which usually indicates my laptop is ready to go). Nevertheless, whenever I'm on a place with a wireless network I've never used (let's say a friend's house). After the desktop appears, the wireless icon on the bottom right corner keeps spinning (as if it's loading) and if I click it to see the available networks the laptop crashes (I'm not talking blue screen here). Now if I wait like 5 - 10 minutes, the Messenger windows will appear, I WILL be able to use my pc as normal (connect to new wireless networks), but during those 5 - 10 minutes, my laptop is completely unusable.

How can I fix this (it also happens at college, where I do have a known wireless network, but that comes from various routers).