October 1, 2009 Update - The issue has been resolved. Please do note the details below as some have mistaken other problems for this.
A quick heads up on an issue we are looking to resolve. Currently if an AOL user is signed in to AIM Express an OC 2007 R2 client will see their presence state but will not be able to initiate an IM to the AOL user. If the user logged in to AIM Express first sends an IM to the OC 2007 R2 client then the conversation is successful.
While we have reproduced this with a few accounts consistently there also some accounts that it does not reproduce with.
No ETA for an update but worth mentioning.