After a lot of testing, I finally came to the conclusion that the plugin named 'msnhandwriting' (In the list of plugins on Messenger plus) is the culprit behind the take-overs. If you have had a popup forced upon you, directing you to
http://blasphemy.killercarrot.co.uk/error.php?a=InkRedist then you may be subject to a lot of future misery. Although I think the host who was providing 'blaspemy' a website, no longer permits this. So I guess they were informed. But just be aware of this. What I recommend; Double click the messenger icon in the taskbar, until the main screen appears. Once this has loaded, click on Plus!>Preferences...>Plugins (Left bottom tab).
From here you can find the plugin and click it once to disactivate it.
You will no longer need to worry about being hi-jacked. But to ensure this, please change your password, secret question and answer.
I am also glad to say that the popup will no longer appear when you open up messenger. Thanks, Shaun.