I installed all of them through BB App World without rebooting until the end but the strange thing is that all of them prompted me for a reboot except Yahoo Messenger. After I rebooted and I clicked on the Yahoo Messenger icon but instead of launching YM, it launched the Blackberry Browser and took me to the Yahoo Messenger download page
http://mobileapps.blackberry.com/dev....do?code=yahoo. All the others launched fine. Instead of downloading from blackberry.com, I went back to the YM page in App World and there was a "reinstall" button at the top of the screen. After reinstalling, it did not prompt me for reboot. It's very strange that only Yahoo Messenger didn't install the first time. Btw, in case anybody is curious about the order in which I installed, I installed AIM, then YM, then Google Talk and lastly Windows Live Messenger.