doccubus_shipper, i suppose that you don't have access to your dad's computer but, if you do, if you can find information in any avast log-files showing what was flagged and why it was flagged, post that..
i would like to see what was flagged and why..
additionally, if it is a case of false-positives, you should let "avast" know about the problem.. in the avast program, on the "support" tab, there is an option, there, for submitting files to "avast".. the option for submitting files is at the bottom of the list, on the "support" tab..