Hey Ben,
Shouldn't it be prompting for elevation when installing into a folder like Program Files, or am I doing something wrong?
Yes, it should, and does, prompt for UAC elevation on all of our test machines.
I've stepped through the code, and ran onto frmMain.OnlyUpdatingLocalUser(). It doesn't seem to catch that the current, non-admin user can't write to the installation folder, and returns false. When I alter the return value to true, elevation is prompted and the installation continues successfully.
Are you running a custom version of wyUpdate? Did you modify the wyUpdate source code in any way? Because "OnlyUpdatingLocalUser()" should return "false" on non-admin accounts. So that function is working correctly and returning the correct value. Did you change how that value is used?
Try using our pre-compiled version of wyUpdate. Does it work as expected?