Users of Avast Antivirus will be finding many of their programs will be falsely showing as infected with a trojan (incl. MailWasher)
This includes other well known programs like Skype, Spybot S&D, Nexus and Copernic for example. This is obviously a false detection (known as a false positive) and at the moment Avast's forums are swamped with people letting them know about it. So we'd like to reassure users that our software does not contain any viruses.
As a workaround until Avast update their definitions -
Right click on the Avast! On-line Scanner Icon in the System Tray (bottom righthand side of screen - the blue one with 'a' in it ) and left click Stop Provider > Standard Shield.
Download MailWasher Pro from here and install again and when MailWasher Pro asks click "Use My Existing MailWasher Pro Settings"
Edit : Avast have now updated their definitions file correcting this problem, so please update those first before trying anything else. To update the Avast database manually right-click on the Avast icon in your system tray and select "Updating" from the menu and then select "iAVS Update". Click it and it will update to the latest version.