Virus Avast doesnt catch

There is a virus in my pen drive which avast 4.7 keeps ignoring but AVG 7.5 catches it. What am I supposed to do? Why doesnt Avast detect the threat? The virus is MntDrCore.exe and there is an autorun.inf that has the following lines:

[AutoRun]
OPEN=MntDrCore.exe
shellexecute=MntDrCore.exe
shell\Open\command=MntDrCore.exe

Very strange that Avast keeps on ignoring this…

There is no application that can find ALL malware. avast is no exception. That is why you have to use multiple applications for security. See http://www.ache.nl

If you find something that avast does not detects, send it to alwil.
How is explained in many other threads.
Use the search option

Which AVG? Antivirus or antispyware?

Can you send the .exe file to avast analysis (virus@avast.com)?