Are you connecting through T-mobile's EDGE service? Neither Apollo or MobileChat work over EDGE while connecting to AIM.
I have both installed on my phone and can only connect to AIM via WiFi. If I connect through T-mobile's EDGE both programs crash. Only MSN seems to work over EDGE.
I connect through internet2.voicestream.com and there was a post on the T-mobile forum here (MMI) where a guy had successfully used both programs through EDGE, but he had to switch to the Total Internet Plan w/ VPN support (
read here). It seems it's a port issue.
I tried changing my plan to the one with VPN support but a rep told me that the iPhone didn't support their VPN network (BS of course). I will be calling them again eventually and force them to give me access to the internet3.voicestream.com (VPN network).