>>It could be it. Although strange thing is that sometimes it works, other times it does not. I think that if Admin forbade the exe to shell out, it would stop running this (shellExcute) all the time.
>>I just asked the user who sent me the error email this morning to reboot her PC. I will see if the problem will be fixed.
>>I am also thinking that I should enclose this call into Try Catch and avoid the user having to see this error.
>>Thank you.
>
>I looked at the code and see that the call to ShellExecutre is already enclosed in Try Catch. And yet, the error occurred and the customer sees the error.

Could it be that some other component that you use also calls ShellExecute()? Anything that, for example, opens a webpage or a pdf, or does something else outside of the app.