Why Concurrency and Object-Oriented model don't play along well with each other

Here is a nice 1h presentation on Concurrency and Concurrent Programs by Brian Goetz:
http://www.infoq.com/presentations/goetz-concurrency-past-present

It explains very well the basics (threads, deadlocks, race-conditions) and the common problems in multi-threaded systems, with some specifics when using Object-Oriented approaches.
Check at the 28 minute mark for the part of why doing concurrency with OO is a pain.
For those of you who are too lazy, here is a screenshot:



On the same topic, you can check this cool chat with Joe Armstrong:
http://channel9.msdn.com/Blogs/Charles/JAOO-2007-Joe-Armstrong-On-Erlang-OO-Concurrency-Shared-State-and-the-Future-Part-1