I have the same problem, but I believe it's caused from a different issue. I am in the process of updating my home, wife's, and kids computers from Norton Antivirus 2003 to Avast. I also have put Avast on two new XP and one XP x64 installations, and all went perfect. However, all of the computers that had Norton (I uninstalled first) won't install Avast properly. Everything works fine, except, and after reading here, that AshDisp.exe won't load. The installer doesn't put it into the "Run" key in the registry. If I click on the .exe, the Taskbar icons load and I can utilize for that "boot run", but after I reboot, the icons don't re-appear, and I have to start all over. I have removed every instance of anything related to "Norton" and "Symantec" in the registry. Norton is notorious for leaving a lot of stuff behind after uninstalling...
I've tried to uninstall Avast, and re-install, but I can't get the installer to properly place ashdisp.exe into the "run" key...and thus a proper installation.
I can't believe that I'm the only one installing Avast after uninstalling Norton...
Any ideas?