This problem is unrelated to Messenger Plus! Live. The error message is telling you there's a problem with the Windows Live Communications Platform, so you need to try and fix it.
Google will help.
#1 - The main cause -
Are you using a skin or theme on your computer? Any kind of visual modification could cause the Windows Live Communications Platform error, as proved
here. Change back to Windows default theme and restart Messenger. Restart if no luck.
#2 - I'll presume you're using Windows XP. If you're using Vista then these instructions will be slightly different to work.
Go to Start > Run
Type in
SFC /scannow and click OK.
This detects whether any of your windows components are missing or damaged, and replaces them with working versions.
You will be required to insert your Windows XP CD.
Once that's done, restart your computer and see if you still have the same problem in Windows Live Messenger.
#3 - Still having the same problem? Someone messaged Windows Live Support
HERE about the problem. Give it a try. Follow exactly as instructed.