Yes that is the thread I was thinking about as it gives a temporary fix download until the next update.
Though I'm not 100% sure this is identical, as if I remember correctly (could well be wrong) crofty59 didn't get this error and I believe he was able to run ashSmpl2.exe. What version do you have, 4.7.942 is the latest ?
You could try the fix it shouldn't hurt, but somehow I don't have much confidence of it working. Then I feel you are down to a reinstall.
Download the avast! Uninstall Utility,
find it here and save it to your HDD so you can find it later.
It would probably be best to download the latest version of avast and save it to your HDD, somewhere you can find it again. Use that when you reinstall.
Then uninstall, reboot, run the uninstall utility, reboot, install the latest version, reboot.