No there is no regular released version, 5.0.655.
I have just done a manual program update and it reports up to date, see image.
So I don't know why yours a) shows 'Secured' yet indicated the program version 5.0.594 with the ! and b) why the update shows a new version available.
Try a repair of avast. Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow. This has in the past resolved this out of sync issue between reported and actual version.
If that has no joy, reboot.