Note that those script warnings have got nothing todo with the scripts themselfs, nor with Messenger Plus!, nor with Windows Live or MSN Messenger...
Also, such warnings exist in extremely many anti-virusses.
What many people forget (or don't alter) is that many anti-virusses are by default set to detect almost anything. In many cases this is just stupid and way to strict for normal computer usage.
_ALL_ anti-virusses can be configured... I suggest to first check your anti-virus settings, learn what they do or don't do. You know, the "setup", "preferences" or "configuration" menus you'll find in almost any program (but which apparently not many actually click on/know about)?
Years ago, the first thing you always did was checking the preferences out, even if you didn't wanted to change anything. You simply checked the various menus and settings out so you knew what the program actually does or can do.
Nowadays, it seems that people just install something without reading anything and be done with it... and then complain something doesn't work, or ask for how they can do something.
What I mean is: if you're anti-virus software (or whatever program for that matter) says something is wrong and you don't understand it why, maybe pressing F1 or going to "help" or "config" might give you faster solutions than anything else...
Anyways, getting off topic here. As for the "this script is suspecious", simply disable that warning/detection in your settings. Especially if it warns you of every script, regardless of what the script does, as that is plain stupid. It is like saying whenever you start the computer: "you're computer is starting, be carefull"...
Security is good and even mandatory, but sometimes it is just too strict/stupid (hence why configuration panels exist in programs! ... use them). Security is far more usefull when you actually know what is or what isn't secured and especially _how_ it is secured.