Download avast! External Control clicking on 'Control' in my signature.
Unzip it and run.
You'll see avast! tweaker option.
Choose to show system tray icon and let us see if it helps.
Another way to fix the problem, just add the path to ashDisp.exe into
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
(as the value named avast!).
Other possibility is adding a link to ashdisp.exe into your startup items.
Are you by any chance using spysweeper?
If so, use the restore/recover or whatever it may be called to restore the deleted registry entry and update your definitions file for spysweeper. It reports incorrectly (false positive) the avast ashDisp.exe which is the icon you see on your system tray.
Other programs that can block are the startup monitors: PrevX, ProcessGuard, WinPatrol, TeaTimer, Ad-watch, etc.
