The avast icon is just an indicator that scans are being done, it rotates and is the interface with the on-access scanners and right click context menu. So it doesn't actually reduce your protection.
What is your Operating System ?
Check Windows Start, Run, type, msconfig - that the startup tab has an entry for ashDisp and that it is ticked.
You need to reread the thread and answer the questions (to yourself and see if they ring any bells) and try some of the suggested solutions.
I don't know where you got the [iAVST] from it is [AAVM], ShowTaskbarIcon=1, however, I think you will find that present.
What other security based software do you have that might block new startup entries, e.g. Spybot S&D (TeaTimer), AdAware (AdWatch), PrevX, WinPatrol, ProcessGuard, etc. ?
As a temporary measure you can create a desktop shortcut for this file C:\Program Files\Alwil Software\Avast4\ashDisp.exe (the avast icon and interface to the providers). Right click on the file and select Send To, Desktop (create shortcut).