In order for us to help you fully we need you to be as accurate and detailed as possible, otherwise we will be groaping in the dark.
The "file name was libsys or similar" does nothing to help, we can't check google, etc. so there is no way to identify if msgfix.exe is a part of or totally different virus, etc.
Please check your avast Log File (right click the avast icon and select avast! Log Viewer and check the warnings section), it should contain the information we asked for.
The reason I asked what you were doing was to try and identify which avast provider detected the virus, if it was web shield then the likelihood is there is nothing on your computer (you said you were on-line). However, in the same paragraph you say you tried to send it to the chest which would indicate it was detected by standard shield, so I'm a little confused too.
The Operating System and location of where it was found are also important as to how it is dealt with. Please re-read my first post and answer all the questions as accurately and fully as possible.
Did you read the thread I gave the link to.
Try not to panic (it doesn't help), I know when you are up to your ass in Alligators it is hard to remember your intention was to drain the swamp.
For the most part it is a waste of time and effort to report IP numbers of an attack but avoid the site, etc. were possible.
If you haven't already got this software (freeware), download, install, update and run it.
1.
Ad-Aware2.
Spybot Search and Destroy3.
Spywareblaster4.
Download HijackThis.zip -
HiJackThis Tutorial