This is actually hard to pinpoint.
We can say that before your computer has loaded files necessary to establish an internet connection, Avast is fully functional.
Avast loads these files at startup: ashmaisv, ashserv, and you will sometimes see ashdisp.
If you run MSCONFIG from the Start/Run utility, and check the tab Startup, you can see in what order and the actual files loaded at startup. Normally, your computer will remember this order and try to keep it unless something in a program causes that program to "hang" a bit and delay it's loading taking it out of order.
The icon IS an indication that the resident scanner (On Access Protection Module) is loaded and active.
If you watch your status bar as programs load, you may notice that the icons load in a different order, and therefore, Avast may load a bit later than the time before, but this is negligible.
My general rule is: If the "hourglass" cursor is still visible, I don't touch the computer. I wait until all my desired programs are loaded and active.
Hope this helps you a bit in understanding the process .
