Wow... I have never had the issue of Yappari hanging up like that.

Right now is hard to tell since the client I have installed in my phone is pretty unstable (it crashes if it receives a message from an unknown contact, it crashes when I press Create Chat, it's totally unusable ).

And also Yappari NEVER takes up to 10-15 seconds to load a chat window. NEVER, except when you press Create Chat immediately after starting Yappari (because it's synchronizing contacts) and even then it is not higher than 5 secs.

Yappari shows a window in 2 seconds max. Maemo SMS Conversations also shows a window in 2 seconds max. I think you're running too much background stuff in your phone that makes it pretty busy?