Hi, welcome to the forums,
Where do you get that "invalid command name" error? if it's in a "amsn error dialog", could you click on the Details button and paste the full details of the bug ?
about aspell, I don't know, maybe it needs to be configured correctly so it can work.
For your hour glass issue, I've heard about it before but we can't do anything about it because it's not coming from our side, you can disable a plugin by doing the following :
Open the finder and go to your HOME -> Library -> application support -> amsn -> <your email>
edit the file plugins.xml with your favorite text editor, find the section for the aspell plugin and change the <loaded>true</loaded> into <loaded>false</loaded>
I hope that helps!