Vb.net – How to remove all traces of a ClickOnce application from a customer’s computer

I have a ClickOnce application that about 120 customers are using. This week, I found out two customers declined an update in January and were stuck on an old version. I discovered this by deleting an ASP script the old versions used on our server. The customers that aren't updating get a 404 and call to ask why.

One customer clicked our install button again and got the latest version no problem. The other clicked our install button and gets an "Application validation did not succeed" error. The details of the error are SomeImage.gif "has a different computed hash than specified in manifest."

I don't want to deploy a new version because that usually results in phone calls asking, "did you add what I asked for yet?"

I figure I should be able to uninstall the application completely and resintall with the one problem user. Nope. The error persists. How can I remove whatever the Windows uninstall process leaves behind that would cause this error to persist?

Update:

I found the folder C:\Users\User\AppData\Local\Apps\2.0 on the customer's Windows Vista computer, and deleted it. We ran the installer again, and the error persisted after redownloading the application. I'm not 100% confident that this folder contained the whole program, though, but it is the only location on disk I could find that contained some resemblance of our application.