Some issues can be fixing just by uninstalling and re-installing WLM. But most errors probably require a registry fix or other settings corrections. You can fix these problems manually. Just visit here or here to find a solution.
However, here is a program designed to help resolve errors more common that can happen by using Windows Live Messenger just by clicking a button. The new version of MSN E-Fix (v. 2.0) supports a greater number of errors and improves compatibility with Windows Vista.
The program does not require any installation. Just run the program, simply select the error you want to repair from the list on the left and click ‘Go’ button and let the program make the necessary corrections.