Recently in a development environment I got an error in AOS that prevent it from starting. After checking the event viewer for a detailed message error, I simply got a generic error message about an invalid assembly.
1) Deleted all files in folder C:\Program Files\Microsoft Dynamics AX\60\Server\MicrosoftDynamicsAX\bin\XppIL.
2) Opened SQL Enterprise Manager and executed the following command “TRUNCATE TABLE SysXppAssembly”. This will delete compilation data.
3) Started AOS Server
4) Run a full CIL compilation.
Voila, AOS is running now smoothly.