It is an odd problem. Try this, make sure your logged in as admin,
1.)un-installing msn, delete all files from - Document and Settings- Administrator- Application Data- Microsoft- MSN Messnger.
2.)Empty all temp folders from, Document and Settings- Administrator- Local Settings- Temp. Also clear all other temp folders, cookies, history, etc....
3.)Reboot. Reinstall messenger and put in your account info. Hopefully this works. If it dont then goto Microsoft support site and post your problem there. They should be able to help you.