Recently, I had an ISV phone me up telling me about an experience they had with a reporting solution. The app was taking some time when it was suppose to print. They could not initially repro the problem.
After some time, they diagnosed that the app was signed with an Authenticode signature. This meant that it went off to the internet to do the verification. If you had a slow line, this could potentially take 60 seconds, and then timeout. The time it took to do the verification would make your app take time to load up.
I saw the exact same thing for a local ISV app when we ran some Windows 7 App Compat Labs.
The good news is that there is a workaround (they found it too). You can add
<configuration> <runtime> <generatePublisherEvidence enabled="false"/> </runtime> </configuration>
to your config file
See http://support.microsoft.com/kb/936707 for more info