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.
I am looking forward to hear about this problem. Saw this a while ago at a customer, but the problem suddenly disappear again :-(
FYI, this issue has been resolved. We followed the solution from this link and it does work. http://blogs.msdn.com/scottos/archive/2009/04/03/resolved-ocs-2007-r2-pic-fails-against-aol.aspx
I am glad Scott's posting helped you but I at this time I do not believe it is the solution for the problem I have attempted to describe. Note that my issue is very specific to the AIM Express client and only when OC 2007 R2 initiates the dialog.
Also in my work with AOL they are investigating an issue that would be fixed.
So for others I would certainly suggest you use Scott's link for complete failure to AOL.
Glad to know we are not the only ones experiencing this issue. Also hit the issue resolved by Scott in our initial deployment, but seems to be a mystery as to why we cannot initiate a session to an AOL AIM Express account. The AOL user can initiate a session to our OCS 2007 R2 users. Would be very interested if anyone has found a solution.