I think Visual studio regularly loses the connection with AX AOS. For this you need to change the VS shortcut properties as follows
Create a new shortcut of Visual studio into your desktop.
Right-click Visual Studio 2010, and select Properties.
Update the Target field and add the /AxConfig switch with either the name of the client configuration or the name of the client configuration file as shown in the following examples:
“C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe” /AxConfig z:\Config\ContosoDev.axc
For this you need to export the AX config file to any of the folder and update the path in the above solution.
Feel free to ask any questions in case you dont get anything.