You will have to hack your registry to fix this problem or just go to the current version of AIM 5.2 instead of the BETA version.
[HKEY_CURRENT_USERSoftwareAmerica OnlineAOL Instant Messenger (TM)CurrentVersionUsersScreenName1Misc]
“ShowAimTodayWindow”=dword:00000000
[HKEY_CURRENT_USERSoftwareAmerica OnlineAOL Instant Messenger (TM)CurrentVersionUsersScreenName2Misc]
“ShowAimTodayWindow”=dword:00000000