Error -41 when installing 5.0 on top of 4.5

[sprezzatura]

I have upgraded my application from using PDF Converter 4.5.1.0 to 5.0.1.9 (DLL version). When I install the new version with 5 on top of an old version that used PDF Converter 4, I get an error -41 ("Wrong Activation Key").

I have to reboot to get it to work OK. If it was the wrong Activation Key in the first place, how come it works the second time after a reboot? BTW 4 and 5 use the same activation key.

This will make for a messy customer experience. How do we avoid this?

[sprezzatura]

Problem solved: a glance at the old & new Activation Codes seemed to indicate they were the same, but they were not. Copying the correct, latest 5.0.1.9 Activation Code to the installer fixed the problem.