While I was messing around with MsgPlus.LogEvent, I found something weird with Plus! Live's Event Log
(contact list menu -> Plus! -> Display Event Viewer)
When you open it, it
always starts as always on top, which isn't too bad in fact. Although, when you click the "Options" menu button, there isn't a check mark next to "Always on top"! If you try to click that option, you unset the always on top behaviour and when you do that again, the check mark appears and the window behaves correctly. But when you close it with always on top unchecked, it still re-opens as always on top.
My suggestion: don't make it always on top on creation, or make the Always on top option save its state to the registry.
Windows Vista Ultimate x64 (6.0.6000)
Windows Live Messenger 8.5.1018
Messenger Plus! Live 4.50.0.312