Avast temporarily disabled when turning on computer

A few weeks ago I noticed the Avast icon was temporarily disabled for a few seconds when I turned on the computer, I ran an anti-malware program which discovered and removed a trojan agent after which everything ran fine. Recently there has been 2 occasions when Avast was temporarily disabled when I’ve switched on and I’ve run anti-malware programs but nothing has come to light. Can anyone advise of any other reasons why Avast may be temporarily disabled? ???

In my Vista system Avast starts very late compared to my Win 7 system at the time of starting the computer.

There is a setting you can change for faster start up but it make your computer a little insecure

Go to settings>troubleshooting and check off “Load Avast! services only after loading other system services”.