Are you both working from the same Hotmail account with the same password or different accounts on the same computer?
Are you running any other email software on your computer? If you are, is there a problem with it also?
In the meantime download and run
ATFCleaner.exe by Atribune. When you access the link given, please read the instructions for your particular browser.
If
ATFCleaner.exe does not help, I would suggest posting a HJT log
here to have your system checked for Malware by our experts.
kind regards,