I've been having a similar problem the past day or so also. When I start up the AIM app, it begins to load but the page stays blank like its trying to log in my aim account and crashes to the homescreen. I found a way to unfreeze it by turning off my 3G/edge signal and turning it back on while in the AIM app (Jailbroken Iphone using SBsettings). When the 3G/edge signal shuts off, the aim app resumes and starts to log in. Once my signal comes back on, the aim app finishes logging in and I am back in business. But once I exit out of the Aim app, I need to follow the same steps to get back in the app. I still receive AIM push notifications even though the app looks frozen.
I tried uninstalling/reinstalling, but that did not resolve my problem. I thought my problem had to deal with me being jailbroken, but it sounds as if we might have a similar situation.
12-27-2009 08:47 PM