I had the same problem.

Sometimes, I can run Task Manager to kill ashdisp.exe and then the boot continue normally.
I haven't been so lucky anytime ...
In the other case, I just have to reset manually the computer. This problem occurs with both configurations. 1 - Windows 2000 SP3 (Athlon 1 GHz). 2 - Windows XP Home SP1 (Pentium 4 2.4 GHz). Is there a solution to this pb ?
My CFG - Athlon XP 2100, 512 MB DDR, XP Proff. SP1 + latest actualization.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run:

atiptaxx.exe - some ATI driver
ashDisp.exe
ashMaiSv.exe
dumprep 0 -k
NeroCheck.exe

What I did is that I moved these two ash*.exe to normal Windows startup folder and after that had this problem no more until new version of Avast restored its settings. I understand that this may downgrade the antivirus power, but it works and is much less painful than resetting more often than every second boot.

to developers : What about to implement some mechanism that will supervise Avast startup process and detect these freezings ? What are the weaknesses of having Avast started from regular startup folder instead of from the “Run” key ? Just to keep the common user’s hands off ?