Guess recently eveyone is sicked of all those spam bots, and their junk notices. Try the following,
1. Download this little addon from http://togu.elementsfree.com/notice.mrc
2. Copy to your mirc folder
3. Type /load -rs notice.mrc in your mirc tool to load the addon.
DONE! All the junk notices will be consolidated into another window, so none of your convos will be affected.
Give it a try, let me know the outcome.