visual studio - ClickOnce Security Zones Installation Bug -

i've run haunting bug. i've built c# application (visual c# 2008 express) , have published in past clickonce application deployed zip file. had no problem installing on our customers' computers several months ago, when attempt install application message @ startup: "application cannot started. contact application vendor." when @ details of message see, "deployment , application not have matching security zones." again, problem doesn't show when installing on second computer, shows 2 of our customers (again, problem did not appear on computers few months ago). because can't replicate problem on own systems, difficult approach, haven't thought of publishing settings before today. here further thoughts:

-there app.manifest file listed under properties in solution explorer didn't seem there earlier in year. i'm not sure why here , whether there should corresponding file when publish this.

-sign clickonce manifests selected.

-enable clickonce security settings selected

-the application full trust application (i toyed around switching "partial trust application" , don't want try unless there high likelihood of resolving this).

-i'm looking fix won't require user make changes on computer. there evidence clearing oneclick cache detailed here (http://codeketchup.blogspot.com/2013/06/how-to-fix-deployment-and-application.html) may work, again intensive fix.

thanks in advance!