I'm using MaxButtons on two sites and in IE8 and lower a string of code is displaying instead of the button. IE 9 seems to be OK. Again, this is for both sites and the plugin is up to date.
I've seen a number of posts in support about conflicts with IE or buttons becoming corrupted, but no responses. Is this plugin still being supported?
http://wordpress.org/extend/plugins/maxbuttons/
Yes, MaxButtons is definitely supported and moving forward - we have more updates coming out soon.
As for versions lower than IE9, we don't make any promises. It's just too time-consuming to do so, sorry. We are aware of a couple of the other issues people have had with IE9 and are working on addressing those.