Not sure what might be going on.
With the mail app open, bring up the "Charms" menu, either by hovering your mouse in the top right corner or by using the WinKey + C, and click "Settings"
Click the accounts link from there and see if both your hotmail and gmail account are listed? If so perhaps try deleting the gmail account (right click it and select delete), close the mail app. Open it again and re-add your gmail account.
Please keep us posted.
Regards
Randy