Upgrade by mail from R5 to R6 on XP - unable to invoke program

After sending out upgrade by mail notices, some users are receiving the error message: “Unable to Invoke Program” when attempting to launch the client setup program. Others users are able to upgrade without a problem. Has anyone run across this issue.

Subject: Upgrade by mail from R5 to R6 on XP - unable to invoke program

We had issues with our Desktop support locking down the registry (as well as other items). For whatever reason, it only affected the XP clients.

Subject: Upgrade by mail from R5 to R6 on XP - unable to invoke program

I have had this problem on Windows 95. The way I got around it is to reboot after doing the the upgrade of the client software. Then you upgrade the mail folders.