Messenger Plus is completly adware free if you so choose. I have never had a problem with spyware being dropped on my PC by MsgPlus and have gone as far as to test it repeatedly by doing re-installs rejecting the sponsor program and then running Adaware, Spybot S&D, Bazooka, HiJack This and have never had any infections on a PC as a result of msgplus. I recomend you un-install msgplus and do a re-install and make sure you selected to no install the sponsor program, I've seen so many people come and say they selected not to install it, but they did, and an uninstall and re-install without it fixed everything.
On a side note, make sure you install MsgPlus from an offical download site (http://www.msgplus.net) to ensure you have the real authentic installer and it hasnt been altered.